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PERSPECTIVES

Reginald Crundall Punnett: First Arthur Balfour Professor of , , 1912

A. W. F. Edwards1 Gonville and Caius College, Cambridge CB2 1TA, United Kingdom

ABSTRACT R. C. Punnett, the codiscoverer of linkage with W. Bateson in 1904, had the good fortune to be invited to be the first Arthur Balfour Professor of Genetics at Cambridge University, United Kingdom, in 1912 when Bateson, for whom it had been intended, declined to leave his new appointment as first Director of the John Innes Horticultural Institute. We here celebrate the centenary of the first professorship dedicated to genetics, outlining Punnett’s career and his scientific contributions, with special reference to the discovery of “partial coupling” in the sweet pea (later “linkage”) and to the diagram known as Punnett’s square. His seeming reluctance as coauthor with Bateson to promote the reduplication hypothesis to explain the statistical evidence for linkage is stressed, as is his relationship with his successor as Arthur Balfour Professor, R. A. Fisher. The background to the establishment of the Professorship is also described.

HE centenary of the foundation of Cambridge Univer- the findings of when these were brought to Tsity’s Professorship of Genetics in 1912 provides a timely light in 1900. He lived, therefore, in a period that was filled occasion to recall the contributions of its first holder, with excitement and could rightly feel that he was involved Reginald Crundall Punnett (1875–1967; Figure 1). Over- in a great adventure that would surely lead to a revolution shadowed by his senior colleague William Bateson (1861– in biological thought.” Crew’s memoirs should be consulted 1926), for whom the Professorship had been intended, and for details of Punnett’s life; here I concentrate on his his successor R. A. Fisher (1890–1962), Punnett played an scientific contributions and give only a brief biographical important role in the early days of Mendelian genetics. He summary. wrote the first genetics textbook Mendelism (Punnett 1905), collaborated in the discovery of partial coupling (linkage), asked G. H. Hardy the question that led to the formulation Brief Biography of what became known as Hardy–Weinberg equilibrium, Punnett was born to George and Emily Punnett (née published Mimicry in Butterflies (Punnett 1915) and Hered- Crundall) at Tonbridge, Kent, on June 20, 1875. Both ity in Poultry (Punnett 1923a), and pioneered the use of sex- parents were of Kentish stock. He was educated at Clifton linked markers for sexing poultry chicks. He founded the School, Bristol, and Gonville and Caius College, Cambridge, Journal of Genetics with Bateson in 1911 and edited it alone which he entered as a scholar in 1895. Originally registering after Bateson’s death. He was the first Secretary and was as a medical student, he took the Natural Sciences Tripos, later President of the Genetical Society of Great Britain. His specializing in zoology in his third year and being placed in name is immortalized in “Punnett’s square” (Figure 2). the first class in the Tripos in 1898. He spent the next year at F. A. E. Crew (Crew 1967) wrote Punnett’s biographical the Naples Zoological Station (Naples, Italy) and at Heidel- memoir for the Royal Society, to which Punnett was elected berg University (Heidelberg, Germany) and in September in 1912, and followed this with a shorter account for 1899 accepted the post of Demonstrator in the Natural His- GENETICS (Crew 1968). In the opening paragraph of the tory Department of the University of St. Andrews (St. latter he said that Punnett “had the good fortune to be an Andrews, Fife, Scotland). In October 1901 a Fellowship of active participant in the work that confirmed and extended Gonville and Caius College followed, capped by the Univer- sity post of Demonstrator in Morphology, which he held un- Copyright © 2012 by of America doi: 10.1534/genetics.112.143552 til 1904, when he became Balfour Student in Zoology. This 1Address for correspondence: [email protected] studentship, in memory of Francis Balfour, Professor of

Genetics, Vol. 192, 3–13 September 2012 3 Figure 2 Punnett’s square, from the Second Edition of Mendelism (Punnett 1907).

carrying out Mendelian experiments at Merton House, Grantchester, [Punnett] wrote to him suggesting that per- haps his nutritional experiments might be so designed that they would yield information concerning the inheritance of coat colour [in the mouse]” (Crew 1967). When Bateson Figure 1 R. C. Punnett. Courtesy of the Master and Fellows of Gonville fi and Caius College, Cambridge. received an offer of nancial support from his friend Mrs. Christiana Herringham in December 1903, he first thought Animal Morphology, Arthur Balfour’s brother, had been held of Leonard Doncaster as an associate, but Doncaster de- by William Bateson from 1897 to 1900. clined (Cock and Forsdyke 2008, p. 217) and so he wrote Then in 1908 Punnett started a rapid rise up the to Punnett (on Christmas Day), inviting him to come “into academic ladder. Still with his Caius Fellowship (which he partnership in my breeding experiments.”“Mr. Punnett was to retain until his death) he became Demonstrator in joined with enthusiasm, and very generously refused Animal Morphology in the Department of Zoology, Superin- the ... salary” (Bateson 1928, p. 87), “... and so a partnership tendent of the Museum of Zoology in 1909, and, when that was to last six years and that was to make notable and Bateson resigned his Professorship of in 1910 to take enduring contributions to genetics came into being. The two up the Directorship of the John Innes Institute, Punnett men were very different temperamentally, Bateson was succeeded to it. In 1912 the Arthur Balfour Professorship of a forceful personality, combative and stern; Punnett was re- Genetics was founded and, following the failure of the tiring, tolerant and friendly; it was a happy and harmonious University to attract Bateson back from his Directorship, partnership” (Crew 1967). Punnett was appointed. We consider the history of the In 1913 Punnett married Eveline Maude Froude, widow Professorship in a later section. of Sidney Nutcombe-Quicke. They lived in Whittingehame At Naples in 1899 Punnett started to study the morphol- Lodge, Storey’s Way, Cambridge, in the house provided for ogy of nemertine (or “Nemertean”) marine worms, and the Arthur Balfour Professor, until Punnett retired in 1940 at these continued to be his main interest at St. Andrews and the age of 65. He and his wife then moved to Bilbrook, near on his return to Cambridge. In 1903 he embarked on a sta- Minehead, Somerset, where he died on January 3, 1967. tistical study “On nutrition and sex-determination in man,” There were no children. using data for London from the 1901 Census, which Crew’s (1967) biographical memoir contains a list of revealed a modest facility in handling numbers (Punnett Punnett’s publications and summaries of his work beyond 1903). The human sex ratio was my own Ph.D. topic and the topics I discuss in detail here. In the summer of 1909 in 1959 I must have heard about his interest and sent him an Punnett had visited Ceylon to study mimetic butterflies, offprint of one of my articles (Edwards 1958) for I still have where he met his Caius colleague R. H. Lock, then Assistant his letter in reply. Director of the Royal Botanical Gardens at Peradeniya Punnett’s association with Bateson started at the begin- (Sri Lanka). The visit led to a handsomely illustrated book- ning of 1904. Some time earlier, “Knowing that Bateson was Mimicry in Butterflies (Punnett 1915). “... it included a

4 A. W. F. Edwards mutationist’s explanation for the of complex mi- metic resemblances between members of unrelated species” (Bennett 1983, p. 8). R. A. Fisher’s view of their evolution was completely different. He set it out in Fisher (1927) and in Chapter VIII, “Mimicry,” of The Genetical Theory of Natural Selection (Fisher 1930a) with special reference to Punnett’s view in the section “The theory of saltations.” Provine (1971, p. 150) gives an account. On evolution Fisher and Punnett were to cross swords again when Punnett reviewed The Genetical Theory, which we refer to below under Popu- lation Genetics. Punnett’s experience with studying Mendelian characters in poultry led him to invent the method of using sex-linked plumage color factors to sex day-old chicks, thus enabling the unwanted majority of cockerels to be disposed of imme- diately. By 1940 he had published, alone or jointly, 11 “Ge- netic studies in poultry,” with another two to come in retirement in 1948 and 1957. Crew (1968) may be referred to for further details, for unlike the biographical memoir for the Royal Society his memoir in GENETICS contains a sub- Figure 3 Punnett’s square, from Report III (Bateson et al. 1906b). stantial extract by Professor F. B. Hutt “whose Genetics of the Fowl is in the direct line of Punnett’s in Poultry, so the two developments went hand in hand. Here we 1923a” (Crew 1968). give the salient features of Punnett’ssquare,relyingon Punnett (1928) edited Bateson’s scientific articles for the extended account by Edwards (2012), which is fully Cambridge University Press. T. H. Morgan (1929) reviewed illustrated. the two volumes in Nature, regretting the omission of the The first published diagrams appeared in 1906. On Reports to the Evolution Committee (see below), which February 1 Bateson, in an address to the Neurological were represented only by summaries. After Bateson’s death Society (Bateson 1906), displayed the 9:3:3:1 Mendelian in 1926, Punnett (1926) wrote a memoir of him in the ratio among the F2 for two loci when dominance is complete Edinburgh Review, part of which was reprinted in Notes at both. Then Report III contained several, notably the ones and Records of the Royal Society in 1952 (Punnett 1952). on p. 3 (our Figure 3) and p. 10. Figure 3 displays the 9:7 ratio obtained when, to quote the figure legend, “The char- acter, colour for example, appears only when C and R meet.” Punnett’s Square We consider the more complex figure on p. 10 in a moment. he work for which Punnett is best remembered, the Figure 3 was repeated by Lock (1906, p. 199) in his book discovery of linkage jointly with William Bateson, arose Recent Progress in the Study of Variation, Heredity, and Evo- out of their studies of Mendelian ratios in the sweet pea lution, the Preface being dated October 23. It will be noted Lathyrus odoratus.Thediscoveryismoreproperlyreferred that these squares are formed by the simple process of laying to as “partial coupling” because the word “linkage” had not out the four gametotypes CR, cR, Cr, cr as headings for both yetbeencoinedinthisconnection,norhaditschromo- rows (paternal gametes, say) and columns (maternal game- somal basis been postulated. The analysis of the various tes) and “adding” them to create the entries in the squares ratios that characterized was much corresponding to the zygotes formed by their unions. facilitated by Punnett’s simple square diagram showing However, when Punnett published the second edition of how gametes combine to make zygotes or sometimes his Mendelism, he used a slightly different format (our Fig- how genotypes at two loci combine to make zygotes. Pun- ure 2; Punnett 1907, p. 45) also displaying 9:3:3:1. It is nett’s square seems to have been a development of 1905, divided into four large squares each of which contains four toolateforthefirst edition of his Mendelism (May 1905) small squares. Each large square is identical in respect to the butmuchinevidenceinReport III to the Evolution Commit- second locus, B,b, and shows the two types of gamete unit- tee of the Royal Society [(Bateson et al. 1906b) “received ing to form zygotes, two of which, Bb and bB, are identical if March 16, 1906”]. The earliest mention is contained in gametic origin is ignored. The four large squares do the a letter to Bateson from dated October 1, same for the first locus A,a, and then the four small squares 1905 (Edwards 2012). We have the testimony of Bateson for B,b are added to each of the large squares for A,a. Of (1909, p. 57) that “For the introduction of this system [the course it comes to the same thing as Figure 3, the difference ‘graphic method’], which greatly simplifies difficult cases, I being only a matter of the labeling. In the third edition am indebted to Mr. Punnett.” As we shall see, 1905 was (Punnett 1911, p. 34) he reverted to the arrangement of also an important year in the discovery of partial coupling, Figure 3 complete with a description of the construction of

Perspectives 5 what he called the “chessboard” method (although in truth it is more like a multiplication table). When three loci are involved, an 8 · 8 square results, as given in Report III on p. 10 (Figure 4). This is an extremely interesting construction. Thinking of it as four large squares, we see that in respect to B,b and R,r, each of these squares is the same, but different from either of the methods of con- structing a two-locus table so far described (in fact there is an error in columns 7 and 8, where the lower entries in row 5 have been interchanged). Instead of the union of gametes we have the union of loci, the rows for R,r, and the columns for B,b. Then each of these squares has been dropped into a square for C,c as in Punnett’s (1907) construction (Figure 2). This hybrid format was suggested by Sir Francis Galton in a letter to Bateson dated October 1, 1905 containing the original of Figure 4 (reproduced in Edwards 2012). It is odd that when it was published, in Report III and later, Galton’s help was not acknowledged. To appreciate the significance of Galton’s arrangement it is necessary to describe the situation that confronted ’ Report III et al. Bateson and Punnett, and since the experiments involved Figure 4 Galton s three-locus square from (Bateson 1906b). are the very ones that led to the discovery of partial cou- pling, this serves as an introduction to the next section. “The work was begun,” wrote Bateson in his book Mendel’s Prin- 524, and 1630 (x2 on 2 d.f. = 4.59, P = 0.10; all values of ciples of Heredity (Bateson 1909, p. 89), “by crossing two x2 quoted here are newly calculated). white sweet peas belonging to the variety Emily Henderson. These plants were alike in every respect so far as could be Partial Coupling (Linkage) perceived, excepting that the shapes of the pollen grains differed, the one having the normal long pollen grains of It is frequently said that linkage was discovered by Bateson the species, while the other had roundish grains. The object and Punnett in 1905. Thus A. H. Sturtevant himself, writing A of the experiment was to trace the descent of the pollen- in retirement (Sturtevant 1965), records character and at the beginning no question of colour was (p. 40) that “Incomplete linkage was first reported in the entertained. When F1 was grown however it was clear that sweet pea by Bateson and Punnett (1905),” but already some here was a remarkable opportunity of studying a reversion qualifications are needed. First, “in the sweet pea” needs to be in color due to crossing, for these plants instead of being in parentheses, or at least between commas, because this was white were purple like the wild Sicilian plant from which the first report of partial linkage in any organism. Second, the our cultivated sweet peas are descended.” reference is actually to Bateson et al. (1905), as given by

Proceeding to the F2, Bateson and Punnett found “phe- Sturtevant in his bibliography, which raises the question of nomena [which] ... presented superficially an appearance the contribution of Saunders. (Morgan 1928, in The Theory of of great complexity. ... It is unnecessary to go through the the , p. 323, went further and omitted Saunders from the long series of steps by which the analysis of the phenomena reference too.) Third, the word linkage in its genetical context was carried out. The meaning of the facts is now perfectly had not, in 1905, been coined and is associated with the clear and they can all be arranged in one consistent scheme” chromosomal theory advanced by Morgan (1911), who even (Bateson 1909, p. 90). They worked out that three loci then still used the term “coupling.” The first use of linkage in would do. The two original whites were CCrrBB and this connection is in 1912 (Morgan and Lynch 1912), but we ccRRbb, leading to F1 all CcRrBb. On selfing, these would should note that Bateson (1906) had written “We have proof lead to the 64 combinations shown in Figure 4. In the pres- that in certain cases a character, say of shape, may be so ence of C (for color?) the situation is always that R (red) linked or coupled with another character, say of color, that dominant to r gives a red flower to which B (blue) dominant all or a majority of the germs [gametes] which carry the one to b adds blue to make a purple flower, although in the carry the other also.” Punnett (1911, p. 87), in the third absence of R there is no blue alone. This is then the pattern edition of his Mendelism,wrote“In some way or other the in the three large squares corresponding to CC, Cc, and cC. factors for blue and for long pollen become linked together in In the fourth, cc, no colors of any kind appear. We end up the cell divisions that give rise to the gametes, but the linking with 3 · 9 = 27 purples, 3 · 3 = 9 reds, and 3 · 4 + 16 = 28 is not complete.” whites. The numbers given in Report III are 1634, 498, and In the present account I use coupling for the statistical 1593, respectively, 3725 in all, against expectations of 1571, evidence as opposed to its chromosomal explanation, and,

6 A. W. F. Edwards like Bateson and Punnett, I distinguish between complete coupling to Bateson and Punnett, omitting Saunders. Al- coupling and partial coupling. This distinction is important, though Saunders was the undoubted Queen of Matthiola, because complete coupling had already been found by Punnett does seem to have been King of L. odoratus. Sturte- Correns (1900) in stocks (Matthiola) as noted by Bateson vant (1965, Author’s Preface, p. xi) had “some direct per- and Saunders (1902), who reported similar “correlation” in sonal contact” with Bateson and Punnett and had met their own experiments with stocks. Correns had used the Saunders, although she counted among those he “never re- word “gekoppelte.” Although this 1902 Report to the Evolu- ally knew.” Bateson (1906), when discussing color in the tion Committee of the Royal Society (Bateson and Saunders sweet pea, refers to “an elaborate series of experiments 1902) was the joint work of Bateson and E. Rebecca made by Miss Saunders, Mr. Punnett, and myself,” but in Saunders (“Becky”), Part I, in which the correlation was the corresponding part of his book Mendel’s Principles of noted, is headed “Experiments with Plants, carried out by Heredity (Bateson 1909, p. 89) he refers to experiments as E. R. Saunders,” to whom therefore we may attribute the having been “carried on jointly by Mr. Punnett and myself observation. for some years.” Nor is there any sense that he is inclined to Partial coupling appears for the first time in Report II to neglect Saunders’ work, for the next section (Bateson 1909, the Evolution Committee (Bateson et al. 1905; received May p. 95) on “Colors of Stocks” (Matthiola) starts “The experi- 18, 1904), the one to which Sturtevant referred. It contains ments of Miss E. R. Saunders have revealed ... .” For further no further reference to correlation in its Matthiola section, information about Saunders see Richmond (2001, 2006) but in the section on sweet peas we read “There is, therefore, and references therein. Lock (1906, p. 200), a member of some coupling of pollen-shape and colors” (italics original) Bateson’s group at the time, says firmly “This phenomenon (Bateson et al. 1905, p. 89). This section is headed “Experi- of partial gametic coupling was discovered by Bateson and ments carried out by W. Bateson, E. R. Saunders, and R. C. Punnett in the Sweet Pea.” Punnett (1914) himself was Punnett (in 1904).” It is evident that many additions to Re- characteristically self-effacing: “Bateson in 1905 was the port II were made after May 1904, including a “Note added first to describe in sweet-peas a remarkable case in which December 1904” at the end. The earliest mention of dis- two characters each exhibiting ordinary Mendelian segrega- turbed segregations corresponding to this coupling is in tion nevertheless showed a peculiar distribution with regard Bateson’s Report to the Committee on Experimental Studies to one another.” Report II refers to “the original crosses of in the Physiology of Heredity at the British Association meet- 1901.” Punnett joined the sweet-pea work in 1904, growing ing in Cambridge in August 1904 (Bateson 1905) and his the F2 in which he and Bateson noted the disturbed segre- Presidential Address to the Zoological Section at the meet- gations, so the F1 must have been 1903, which would make ing (also reproduced in Bateson 1928; the mention is on p. the original cross 1902. Perhaps there were some in both 255). 1901 and 1902. Then in Report III (Bateson et al. 1906b; received March In his reminiscences “Early days of genetics” given at the 16, 1906) there is a full section on “Gametic Coupling,” hundredth meeting of the Genetical Society at Cambridge in which starts “Early in the revival of breeding experiments, 1949, Punnett (1950) said “Sweet peas were the other main attention was called, especially by Correns, to the phenom- line of inquiry. We grew some thousands each year and of enon of coupling between characters. .... Examples of partial course the garden at Merton House [the Bateson home in coupling have not hitherto been adequately studied. A re- Grantchester] could not nearly accommodate such num- markable case occurs in regard to the distribution of the bers.” He goes on to describe the additional plots on the pollen-characters in F2 from the white long x white round University Farm at Impington, four miles away, and the ride Sweet Pea” (Bateson et al. 1906b, p. 9), and the results are there “for a long afternoon, Bateson with his wife in the printed. More information is given in the later section of trailer carrying the ‘Farm Book’ and a microscope.”“One Report III devoted to the sweet pea itself (“Experiments by of us pulled the plant and sung out its characters and W. Bateson, E. R. Saunders and R. C. Punnett”). The crucial handed the plant to the other, who, with the microscope results had in fact appeared earlier in a brief note in Proceed- perched on some odd box picked up at the farm, determined ings of the Royal Society, Series B (Bateson et al. 1906a; re- the shape of the pollen. All duly logged by Mrs. Bateson” ceived December 1 and read December 7, 1905). (Punnett 1950). Finally, Report IV (Bateson et al. 1908) contains, in its The “Farm Books” and allied notebooks recording exper- introduction, a brief review of work on partial coupling, imental data are preserved in Cambridge University Library which starts “The majority of our Sweet Pea work of the and might provide further information about the partici- past two seasons was undertaken with a view to further pants, if only by the handwriting. But no doubt they all elucidating the phenomenon we have termed gametic cou- helped each other, and it looks as though Mrs. Bateson de- pling” (Bateson et al. 1908, p. 2). The section on sweet peas served a formal mention too. is headed “Experiments by W. Bateson and R. C. Punnett” Bateson and Punnett found an F2 segregation 2844 long and contains a subsection “Partial Gametic Coupling.” pollen and 881 round, against 3:1 expectations of 2794 and There is some slight evidence that Sturtevant, in his His- 931, respectively (x2 on 1 d.f. = 3.62, P = 0.057). As we tory, might knowingly have credited this discovery of partial have seen, in the field they scored the color before the

Perspectives 7 fl pollen type so it would be natural to have three columns for Table 1 F2 segregation in the sweet pea for ower color the colors, each divided into two for the pollen type, and this and pollen type is how the data were presented in Report III (Table 1). They Purple Red White noted that the 3:1 ratio did not hold for the three color types Long Round Long Round Long ound individually. There seemed to be some kind of coupling of 1528 106 117 381 1199 394 round with red and long with purple that was disturbing the Mendelian segregations; white seemed to be unaffected. u Bateson and Punnett’s explanation was that B (blue) and L with the simpler , they would have been free to choose the (for long) tended to associate in the gametes, as did their best value without restriction. As late as March 1911, the date recessive counterparts b and l (round). The converse to this of the Preface to his third edition of Mendelism, Punnett writes “ coupling was the “repulsion” of B and l, b and L. (Punnett 1911, p. 87) Nor for the present can we suggest why They were familiar with Mendel’s law of independent certain factors should be linked together in the peculiar way segregation and with the complete coupling reported by that we have reason to suppose that they are during the pro- ” Correns and by Saunders, but here was something in be- cess of the formation of the gametes. ’ tween, partial coupling. “The significance of such partial Weldon (1902) had already applied s fi ’ coupling is obscure, and it may result from several pro- goodness-of- t test to Mendel s data, so that Bateson and fi cesses, between which no discrimination can yet be made” Punnett could have chosen the value that gave the best tby x2 (Bateson et al. 1906b, p. 9) (Report III). But it could be the criterion of , thereby inventing the method of mini- x2 measured, and Bateson and Punnett found that if gametes mum nearly a decade before Engledow and Yule (1914) were produced in the ratio 7BL:1Bl:1bL:7bl, the resulting did so (reprinted with a commentary by Edwards 1997). But ’ phenotypic ratio 177BL:15Bl:15bL:49bl fitted the observed that would have been stealing the biometricians clothes. numbers (Table 1) quite nicely. The calculation of the phe- We conclude by noting that Punnett made a very pre- scient remark about partial coupling when addressing the notypic ratio from the gametic for an F2 segregation is now an elementary student exercise, but Report III did not ex- Epidemiological Section of the Royal Society of Medicine on ’ plain it, and neither did Bateson (1909) in his book. The February 28, 1908, 3 years before Morgan s chromosomal “ general result for the gametic ratio linkage theory. Enough, however, is known to make it cer- tain that it [partial coupling] often plays an important part ðn 2 1Þ BL:1Bl:1bL : ðn 2 1Þbl in heredity, and I have laid some stress upon it because it may eventually be found to throw light upon the alleged was given in Report IV (Bateson et al. 1908) and by Punnett association of certain physical peculiarities in man with par- in the third edition of Mendelism, with a full explanation for ticular forms of disease” (Punnett 1908). The comment fore- the above case (Punnett 1911, Appendix to Chap. IX, p. 88): shadows the suggestion by Fisher (1935) in “Linkage studies and the prognosis of hereditary ailments” read to the Inter- 2 2 ð 2 Þ : ð 2 Þ : ð 2 Þ : 2 2 ð 2 Þ : 3n 2n 1 BL 2n 1 Bl 2n 1 bL 3n 2n 1 bl national Congress on Life Assurance Medicine (see Edwards 2004, for Haldane’s possible contribution), which in turn (In fact, Punnett has a sign wrong in the gametic ratio.) foreshadowed the similar suggestion by J. H. Edwards Following Bridges (1914), nowadays we would use the re- (Edwards 1956) in connection with detecting marker loci combination fraction u =1/n with the gametic ratio in amniotic cells. For if a disease gene is linked closely enough to a marker locus, knowledge of the marker geno- 1 1 1 1 ð1 2 uÞ: u : u : ð1 2 uÞ type may help in the prognosis of a disease not yet manifest. 2 2 2 2 Punnett also remarked, in 1907 (Mendelism; Punnett 1907, “ to give the familiar p. 64), that there is every probability that, as it [partial coupling] becomes better known, it will be found of peculiar 1 1 1 1 1 1 1 importance in the elucidation of the architecture of the gam- þ ð12uÞ2: u 2 u2 : u 2 u2 : ð12uÞ2: 2 4 2 4 2 4 4 ete.” In his last edition (Punnett 1927, p. 135) he reminded us of this by quoting it, adding “How brilliantly this pre- fi Alas, it did not occur to Bateson and Punnett that the “sev- diction has been ful lled by Professor Morgan and his eral processes” they could contemplate for the explanation of colleagues will appear in the following chapter [the chro- ” partial coupling need not be limited to integral values of n,and mosome theory]. they became fixated on the further idea that n had to be a power of 2 [“pure numerology brought about by a fixation The Reduplication Hypothesis on Mendelian ratios” (Edwards 1996)], for they began to visualize processes of gametogenesis that required this as For many years neither Bateson nor Punnett accepted the an explanation, their so-called “reduplication” hypothesis chromosomal explanation of linkage, and by “coupling” and (BatesonandPunnett1911;seebelow).Iftheyhadkeptan “repulsion” they meant statistical associations as observed in open mind and allowed any value of n, or better still worked the sweet pea. In a talk in 1959 Punnett said “I have

8 A. W. F. Edwards sometimes been asked how it was that having got so far we GENETICS, Vol. 191, Num. 2). Morgan was to write, in The managed to miss the tie-up of linkage phenomena with the Theory of the Gene (Morgan 1928, p. 41) “From the nature of . The answer is Boveri. We were deeply the case it is practically impossible to demonstrate, even impressed by his paper ‘On the Individuality of the Chromo- when twisting of the chromosomes is admitted, that it actu- somes’ and felt that any tampering with them by way of ally leads to an interchange of the kind demanded by the breakage and recombination was forbidden” (Punnett genetic evidence.” 1950). In 1911 they advanced their “reduplication” hypoth- What did Punnett really think? According to Cock (1983) esis to explain coupling and its mirror phenomenon, repul- “At no time did Punnett show any great interest in chromo- sion. Its origin can be seen in some comments by Bateson in somes,” and I suspect that Punnett, who possessed “a blithe, Mendel’s Principles of Heredity (1909, pp.157–161), but the kindly, open-air personality” (Needham 1967) quite unlike definitive account is in Bateson and Punnett (1911). By the the combative Bateson, might simply have opted for a quiet time Whitehouse (1965) wrote his magisterial Toward an life. Cock (1983) continued “He is unlikely, therefore, to Understanding of the Mechanism of Heredity it had been for- have given Bateson any stimulus toward a more favorable gotten. We use Sturtevant’s (1965) historical account: view of theory.” There is also the possibility that he was sensitive to the view of his friend Lock, who According to the reduplication hypothesis, segregation does not occur at the time of meiosis but somewhat earlier, had suggested as early as 1906 (Lock 1906, p. 252) that “ and not necessarily at the same time for each pair of . coupling might be due to some mechanism which causes The cells that are finally produced, each with a single set of the representative particles of the respective characters con- genes, then multiply at different rates to give the observed cerned to remain in company during the process by which ratios. It is not easy to see why this scheme was developed, the other allelomorphs are being reassorted between the since there is nothing in it that seems related to the (2n– chromosomes,” as had been noted by Morgan and his col- 1):1 series, nor is there any independent evidence for the leagues (Sturtevant 1965). Even when describing the complex and symmetrical pattern of divisions that it zygotic ratios arising from gametic coupling in his 1919 ’ requires. The hypothesis is related to Bateson s reluctance edition of Mendelism, Punnett (1919, p. 124) does not de- to believe that segregation occurs at the meiotic divisions scribe the reduplication hypothesis, merely saying “More (Sturtevant 1965, p. 40). recently the term ‘reduplication’ has been brought into Sturtevant continues with further comments on Bateson’s use. .... The term is not altogether satisfactory, for thinking. For more information about the hypothesis and are not at present in agreement as to the manner in which Bateson’s reluctance to accept the chromosome theory see these gametic series come to be formed.” Torn between Cock (1983), who, interestingly, headed his section on it Bateson and Lock, it would have been charactistic of Punnett “Bateson’s own rival theory,” and Cock and Forsdyke to have kept his head down, and in any case from 1911 (2008). The best that can be said for the theory is that it Bateson was at the John Innes Institute and not in Cambridge. seems to have spurred Morgan on to have his eureka mo- ment in 1911 with the chromosomal explanation of linkage. The Arthur Balfour Professorship of Genetics Punnett himself never incorporated reduplication into the later editions of his Mendelism, limiting his discussion to The prehistory of the Arthur Balfour Professorship starts not observations on the numerical ratios thought to be occur- with Punnett, but with Bateson, whom the University made ring. He pursued the question with further experiments in a Reader in 1908. In their Report the recommending body, sweet peas (Punnett 1913, 1917a), but by the second of the General Board, had said that “they regret that in view of these articles he was already considering Morgan’s explana- the state of University finances they cannot propose at the tion of linkage, and in the fifth edition of Mendelism present time to establish a Professorship in Heredity and (Punnett 1919, p. 133) he introduced a new chapter, “The Variation” (Cambridge University Reporter 1907–1908, p. Chromosome Theory”“to present the position of the sup- 213). The academic and political background to this ap- porters of the chromosome theory ... [which] is, at the pre- pointment is fully described by Cock and Forsdyke (2008, sent moment, the most keenly discussed question in p. 303). Evidently wheels were turning behind the scenes, heredity.” But the controversy was not really being discussed for on February 24, 1908 the University’s Council was able any more, and one senses that his heart was not in redupli- to publish a report “on a proposed Professorship of Biology” cation and he simply did not want to upset Bateson. (Cambridge University Reporter 1907–1908, p. 632; reprin- Bateson (1922) famously abandoned his doubts “after ted in part in Cock and Forsdyke, p. 306). An anonymous a week in close communion with the wonders of Columbia benefactor, likely to have been Arthur Balfour, had offered to University” visiting Morgan’s laboratory. The observations of support in part a Professorship to be devoted to “that branch the Belgian cytologist F. A. Janssens published in 1909 had of Biology now entitled Genetics (Heredity and Variation)” persuaded Morgan and most other people of the existence of for 5 years in connection with the celebration of the Darwin crossing-over sufficient to account for the observed linkage centenary in 1909. Indeed, he wanted it to be the “Darwin phenomena, even though doubt remained about Janssens’ Professorship,” but the Council thought a title should wait precise model (see the Perspectives by Koszul et al., 2012, in until “the professorship can ... be placed on a permanent

Perspectives 9 footing.” The duty of the Professor was quite specific: “to was held at Balfour’s house in London, as a result of which promote by teaching and research the knowledge of Genet- an anonymous benefactor placed in the hands of Balfour’s ics.” It was less than 3 years since Bateson had coined the friend Viscount Esher the sum of £20,000 to endow a Pro- word. The Professorship was clearly intended for him, and fessorship to be called the Balfour Professorship of Genetics his election was announced on June 8. He gave his Inaugu- (Cambridge University Reporter 1911–1912, p. 694). Regu- ral Lecture “The Methods and Scope of Genetics” on October lations were drawn up, which stipulated that the initial ap- 23 (Bateson 1908) and it is from 1908 that Cambridge’s pointment should be made by Balfour and the Prime Professorship of Genetics really dates. For Punnett the “mu- Minister jointly. It was also decided that the title should be sical chairs” of posts led to the changes already mentioned in the Arthur Balfour Professorship to avoid confusion with the biographical section above, culminating in his election to Francis Balfour. this Professorship of Biology when Bateson resigned it to Balfour wrote to Bateson, inviting him to accept the take up the Directorship of the new John Innes Horticultural Professorship, but Bateson, unwilling to return from his Institute in 1910. Directorship of the John Innes Institute, declined and Arthur James Balfour (1848–1930) was Prime Minister suggested that Punnett “is in every way worthy to be from 1902 to 1905, a brilliant aristocratic intellectual who appointed” (Cock and Forsdyke 2008, p.386). And so he held a key position in the Conservative party for nearly fifty was, on November 11, 1912, being formally admitted at years. He was the elder brother of Francis Balfour, who had the Congregation on November 22. Whittingehame Lodge, lost his life in a climbing accident in 1882 soon after becom- the Professor’s house, was presented to the University in ing Cambridge’s Professor of Animal Morphology. He had 1914 by Viscount Esher and Arthur Balfour, by then an Earl. taught the undergraduate Bateson. Arthur Balfour’s many Punnett’s legacy to Cambridge University as Professor connections included his brother-in-law Lord Rayleigh, was modest. When his successor R. A. Fisher was elected Chancellor of the University at the time of the Darwin Cen- in 1943, he found no staff and no students, but the large tenary, an office to which he himself succeeded in 1919. He house, Whittingehame Lodge, intended for his occupation. was President of the British Association at the time of the “With the coming of war, the house was let to tenants and 1904 Cambridge meeting and the foundation President of the land plowed up by the War Agricultural Committee. The the Genetical Society in 1919, being succeeded on his death department ceased to exist” (Box 1978, p. 398). Fisher was by Punnett. Among his undergraduate friends he counted able to live in Caius College, since his Fellowship had been George Darwin, with whom he played real (“court”) tennis, renewed on his return to Cambridge. Between 1943 and his and George had taken him to visit his father retirement in 1957 he used the house and garden to develop at his house in Downe, Kent. “The kindness of the great a small Department and start a third-year Natural Sciences man, his sympathy and charm, exceeded all that could be Tripos subject, “Genetics.” Nowadays the Department thr- demanded by the most self-centered guest, and left a deep ives, and one valuable direct legacy of Punnett’s remains impression on my youthful mind” (Balfour 1930, p. 38). to this day: his collection of offprints and many of his books. Bateson could not have had a more powerful friend at court However, Punnett influenced the young Fisher, who was than Arthur Balfour. a student in Caius College in 1909–1913 during which time During the 1909 Cambridge Darwin celebrations Balfour he helped to found the Cambridge University So- was chosen to propose Darwin’s “immortal memory” at the ciety, approaching Punnett, one of the dons who was a mem- banquet on June 23. That morning the Chancellor, Lord ber of the national Society, to serve on its Council. Punnett Rayleigh, had ended his address of welcome to the delegates gave a lecture at the second public meeting of the University by saying Society on December 5, 1911. “The undergraduate commit- tee of the Society found Punnett’s exposition of Mendelism During the last generation, Cambridge, especially since so important that, at a meeting in Fisher’s rooms [in Caius] the time of Michael Foster, has been active in biological work. We have the men and the ideas, but the difficulty has the following term, Fisher as chairman proposed that they always been lack of funds. At the present time it is desired, should make it a rule that each academic year one paper among other things, to establish a Chair of Genetics – a sub- be devoted to an elementary exposition of the principles ject closely associated with the name of Darwin and of his of heredity, meaning, of course, Mendelism” (Mazumdar relative Francis Galton, and of the greatest possible impor- 1992, p. 99). tance, whether it be regarded from the purely scientificor from the practical side. I should like to think that the in- From 1920 to 1926 Fisher was a Fellow of Caius at the terest aroused by this Celebration would have a practical same time as Punnett and though not resident he would outcome in better provision for the future cultivation, in his have met him frequently. It was Punnett who, with Karl own University and that of his sons of the field wherein Pearson, reported unfavorably for the Royal Society on – Darwin labored (Cambridge University Reporter 1908 Fisher’s (1918) famous article “The correlation between rel- 1909, p. 1372). atives on the supposition of Mendelian inheritance,” The plea did not fall on deaf ears. In July 1910 Balfour prompting Fisher to remark to W. F. Bodmer in 1956 “My wrote a short article dealing with the endowment of the 1918 paper was refereed by Pearson and Punnett, both of study of Genetics in the University. Late in 1911 a meeting whom I later succeeded” [personal communication; see also

10 A. W. F. Edwards Fisher’s letter to C. S. Stock, November 18, 1943, replying to with weightless elephants upon frictionless surfaces, where Stock’s letter congratulating him on election to the Arthur at the same time we are largely ignorant of the other prop- Balfour Professorship (Bennett 1983, p. 264)]. All things erties of the said elephants and surfaces.” It was not to be considered, Fisher did not have a high academic opinion expected that a man of such opinion would, only a dozen of his predecessor. I give some of the reasons for this below. years later, be able to offer an informed assessment of The Punnett had gone to his Somerset retirement before Fisher Genetical Theory, and Punnett seemed to admit as such: returned to Caius, and although they overlapped as Fellows “Probably most geneticists to-day are somewhat skeptical until Fisher died in 1962, Punnett did not return often and as to the value of the mathematical treatment of their prob- there is no corporate memory of their interaction when he lems. With the deepest respect, and even awe, for that as- did. sociation of complex symbols and human genius that can bring a universe to heel, they are nevertheless content to let it stand at that, believing that in their own particular line Population Genetics it is, after all, plodding that does it.” wrote The story of Punnett’s friendship with the mathematician G. to Fisher “I am rather sorry they picked out an old discon- H. Hardy and how it led to Hardy’s 1908 discovery of “Hardy– tinuous stick-in-the-mud like Punnett to review you in Na- Weinberg equilibrium” at the same time as W. Weinberg’shas ture. But to get 5 columns is an excellent advertisement. My often been told, not always correctly. In itself it reveals little of father would have been much pleased with such a review of Punnett except that he was puzzled by something that really the Origin, and merely carefully noted the points to answer is extremely simple, and he had to get Hardy to set him in his next edition. I think you may be well pleased. I never straight. The fullest and, I hope, most accurate, account is had so long a review” (Bennett 1983, p. 131). to be found in a recent Perspectives (Edwards 2008). In the review Punnett advanced his mutationist position: Later, when writing his book Mimicry in Butterflies, “Throughout the book one gets the impression that Dr. Punnett (1915) appealed to Hardy for some more mathemat- Fisher views the evolutionary process as a very gradual, ical help. He wanted to know the effects of selection at a single almost impalpable one, in spite of the discontinuous basis Mendelian diallelic locus under random mating, and Hardy, upon which it works.” He touches on melanic moths, on perhaps aware of the amount of computation involved, passed poultry, and on mimicry, subjects on which he was well in- the problem on to his Trinity pupil H. T. J. Norton. The results formed as a naturalist, and ends up by complaining about were published in tabular form in Appendix I of Punnett’s Fisher’s English. Bennett (1983, p. 35) reports that the re- (1915) book (and reprinted in Provine 1971). They were very view “was a great disappointment to Fisher,” but one won- influential, among other things inspiring J. B. S. Haldane to ders whether the disappointment was more over the choice initiate his long series of articles on selection. Haldane was of reviewer than the content, because Fisher knew Punnett appointed Reader in Biochemistry at Cambridge in 1923, with well enough not to have expected anything else from him. a Fellowship of Trinity, and wrote that in 1922 Norton had Fisher’s response listed six points (“misstatements or other shown him some calculations that were eventually published slighter misrepresentations”), and Punnett attempted to an- in 1928 (Haldane 1927; Norton 1928). Provine (1971) may swer them. The exchange served only to emphasize the be consulted for further details and Charlesworth (1980) for magnitude of the scientific gulf that separated the first two details of “Norton’s theorem.” holders of the Arthur Balfour Professorship of Genetics. In 1917 Punnett again sought Hardy’s help over a similar problem, and this time Hardy himself calculated how slowly Conclusion a recessive lethal is eliminated from a population, thus ap- parently discrediting the eugenicists’ claim that deleterious Reginald Crundall Punnett owed his academic career and recessives could be eliminated in a few generations (Punnett reputation to the good fortune of being invited by William 1917b). However, Fisher (1924) countered that these calcu- Bateson to join him as his partner in undertaking breeding lations “have led to a widespread misapprehension of the experiments in both plants and animals in the heady days effectiveness of selection.” that followed the rediscovery and appreciation of Mendel’s Punnett (1930a) reviewed The Genetical Theory of Natu- article at the beginning of the 20th century. Having made ral Selection (Fisher 1930a) for Nature. It was not friendly. a signal contribution to these studies his good fortune con- Fisher (1930b) replied in a letter to Nature, to which the tinued when he found himself the natural alternative to editor allowed Punnett (1930b) an immediate rejoinder. We Bateson to occupy the Arthur Balfour Professorship of Ge- now know, what Fisher could not have known at the time, netics at Cambridge when Bateson declined it. Thereafter he exactly what Punnett reported to the Royal Society about lived the comfortable life of a Professor between the wars, Fisher’s “1918” article (Norton and Pearson 1976): “I have provided with a house by the University, a Fellowship by his had another go at this paper but frankly I do not follow it College, and the absence of pressing duties by either. owing to my ignorance of mathematics.” He ended “I do not But one should not belittle the diagram that bears his feel that this kind of work affects us biologists much at name, any more than one should belittle Venn’s famous logic present. It is too much of the order of problem that deals diagram, just because it is simple. It served a need so well that

Perspectives 11 it is difficult to see how the complex pattern of inheritance of Bateson, W., 1905 Report of the 74th meeting of the British Asso- flower color in the sweet pea could have been unraveled ciation for the Advancement of Science, Cambridge, August 1904. without it. The discovery of partial linkage depended on the Murray, London. “ Bateson, W., 1906 An address on Mendelian heredity and its ap- knowledge thus gained. Bateson (1909, p. viii) wrote In plication to Man. Brain 29: 157–179. Reprinted in Bateson, B. 1904 I had the good fortune to gain Mr. R. C. Punnett as (1928, pp. 181–200). a partner. Since that date we have worked in close collabo- Bateson, W., 1908 The Methods and Scope of Genetics. Cambridge ration, and the work that we have thus done has been in University Press, Cambridge/London/New York. Reprinted in Bateson, B. (1928, pp. 317–333). every sense a joint product, both as regards design, execution, ’ ” Bateson, W., 1909 Mendel s Principles of Heredity. Cambridge Uni- and interpretation of results. But he was careful to attribute versity Press, Cambridge/London/New York. the diagram to Punnett, as we have noted. Bateson, W., 1922 Evolutionary faith and modern doubts. Science G. Evelyn Hutchinson (Hutchinson 1979) remembered 55: 55–61 and Nature 109: 553–556. Reprinted in Bateson, B. from his undergraduate days: (1928, 389–398). Bateson, W., and R. C. Punnett, 1905; see, Bateson, Saunders and Genetics was taught twice a week, at five o’clock in the Punnett (1905). Michaelmas term, by R. C. Punnett .... He was a mild man Bateson, W., and R. C. Punnett, 1911 On gametic series involving with an overdominant wife who had been a major tennis reduplication of certain terms. J. Genet. 1: 293–302. player. Her opponents must have been terrified. Punnett Bateson, W., and E. R. Saunders, 1902 Experimental Studies in the had fine collections of Chinese porcelain and Japanese Physiology of Heredity (Reports to the Evolution Committee of prints in a delightful house backed by an experimental the Royal Society, Report I), pp. 3–160. garden, and he devoted himself largely to the genetics of Bateson, W., E. R. Saunders, and R. C. Punnett, 1905 Experimental sweet peas. The Punnetts gave Sunday lunches with superb Studies in the Physiology of Heredity (Reports to the Evolution wine to an incongruous set of students, half biological Committee of the Royal Society, Report II), pp. 4–99. intellectuals, half athletes, all I think men. Only about half Bateson, W., E. R. Saunders, and R. C. Punnett, 1906a Further a dozen students took Punnett’s course. ... The chromo- experiments on inheritance in sweet peas and stocks: prelimi- some theory was still widely debated. Bateson was usually nary account. Proc. R. Soc. Lond., B 77: 236–238. skeptical, though I know he accepted it for about a fortnight Bateson, W., E. R. Saunders, and R. C. Punnett, 1906b Experimental before his death. Punnett tended to be more receptive to Studies in the Physiology of Heredity (Reports to the Evolution the idea. One evening the high point of the course arrived Committee of the Royal Society, Report III), pp. 2–53. unexpectedly; Punnett came in demurely and then an- Bateson, W., E. R. Saunders, and R. C. Punnett, 1908 Experimental nounced that he had just finished all the calculations of Studies in the Physiology of Heredity (Reports to the Evolution linkage of the various characters he had studied in the Committee of the Royal Society, Report IV), pp. 2–18. sweet pea and that indeed there were as many linkage Bennett, J. H. (Editor), 1983 Natural Selection, Heredity, and Eu- groups as chromosomes. The chromosome theory had genics. Including selected correspondence of R. A. Fisher with Leo- worked for a plant as well as an animal and therefore nard Darwin and others. Clarendon Press, Oxford. might reasonably be expected to be of general validity Bridges, C. B., 1914 The chromosome hypothesis of linkage ap- (Hutchinson 1979, p. 99). plied to cases in sweet peas and primula. Am. Nat. 48: 524–534. Box, J. F., 1978 R. A. Fisher: The Life of a Scientist. Wiley, New Punnett’s paper reporting this is Punnett (1923b). York. But I leave the last word to Joseph Needham (Needham Charlesworth, B., 1980 Evolution in Age-Structured populations. 1967), the Master of Caius: “Punnett also had a highly schol- Cambridge University Press, Cambridge/London/New York. ’ arly side, being greatly interested in the and Cock, A. G., 1983 William Bateson s rejection and eventual accep- tance of chromosome theory. Ann. Sci. 40: 19–59. possessing a notable library of its seventeenth and eighteenth- Cock, A. G., and D. R. Forsdyke, 2008 Treasure Your Exceptions: century literature. Unfailingly helpful and charming to youn- The Science and Life of William Bateson. Springer-Verlag, New ger colleagues, he would present them sometimes with rare York. books, and encourage them in their work in ways which they Correns, C., 1900 Ueber Levkojenbastarde. Botanisches Central- – could never hope to repay. We greatly cherish his memory and blatt 84: 97 113. ” Crew, F. A. E., 1967 Reginald Crundall Punnett. Biogr. Mem. Fel- record this for the information of later generations. lows R. Soc. 13: 309–326. Crew, F. A. E., 1968 R. C. Punnett. Genetics 58: 1–7. ’ Acknowledgments Edwards, A. W. F., 1958 An analysis of Geissler s data on the human sex ratio. Ann. Hum. Genet. 23: 6–15. I am grateful to Peter O’Donald for the reference to Hutch- Edwards, A. W. F., 1996 The early history of the statistical esti- – inson (1979) and to Axel Zeitler for help in understanding mation of linkage. Ann. Hum. Genet. 60: 237 249. Edwards, A. W. F., 1997 Three early papers on efficient paramet- Correns (1900). ric estimation. Stat. Sci. 12: 35–47. Edwards, A. W. F., 2004 Mendelism and man 1918–1939, pp. 33– 46 in A Century of Mendelism in Human Genetics,editedbyM. Literature Cited Keynes, A. W. F. Edwards, and R. Peel. CRC Press, Boca Raton, FL. Edwards, A. W. F., 2008 G. H. Hardy (1908) and Hardy–Weinberg Balfour, A. J., 1930 Chapters of Autobiography, edited by E. Dugdale. equilibrium. Genetics 179: 1143–1150. Cassell, London. Edwards, A. W. F., 2012 Punnett’s square. Stud. Hist. Philos. Biol. Bateson, B., 1928 William Bateson, Naturalist. Cambridge Univer- Biomed. Sci. 43: 219–224. sity Press. Reprinted in Cambridge Library Collection, Cam- Edwards, J. H., 1956 Antenatal detection of hereditary disorders. bridge University Press, 2009, Cambridge/London/New York. Lancet 270: 579.

12 A. W. F. Edwards Engledow, F. L., and G. U. Yule, 1914 The determination of the Provine, W. B., 1971 The Origins of Theoretical Population Genet- best value of the coupling-ratio from a given set of data. Proc. ics. Chicago University Press, Chicago. Camb. Philos. Soc. 17: 436–440. Punnett, R. C., 1903 On nutrition and sex-determination in man. Fisher, R. A., 1918 The correlation between relatives on the sup- Proc. Camb. Philos. Soc. 12: 262–276. position of Mendelian inheritance. Trans. R. Soc. Edinb. 52: Punnett, R. C., 1905, 1907, 1911, 1919, 1927. Mendelism. Macmil- 399–433. lan, London. Fisher, R. A., 1924 The elimination of mental defect. Eugen. Rev. Punnett, R. C., 1908 Mendelism in relation to disease. Proc. R. 16: 114–116. Soc. Med. 1: 135–168. Fisher, R. A., 1927 On some objections to mimicry theory: statis- Punnett, R. C., 1913 Reduplication series in sweet peas. J. Genet. tical and genetic. Trans. R. Entomol. Soc. Lond. 75: 269–278. 3: 77–103. Fisher, R. A., 1930a The Genetical Theory of Natural Selection. Punnett, R. C., 1914 Mendelism in Great Britain. J. Hered. 5: 86– Clarendon Press, Oxford. Ed. 2, Dover, New York (1958); var- 89. iorum edition, Oxford University Press, Oxford (1999). Punnett, R. C., 1915 Mimicry in Butterflies. Cambridge University Fisher, R. A., 1930b Genetics, mathematics, and natural selection. Press, Cambridge/London/New York. Nature 126: 805–806. Punnett, R. C., 1917a Reduplication series in sweet peas II. J. Fisher, R. A., 1935 Linkage studies and the prognosis of heredi- Genet. 6: 185–193. tary ailments. Transactions of the International Congress on Life Punnett, R. C., 1917b Eliminating feeblemindedness. J. Hered. 8: Assurance Medicine, London. 464–465. Haldane, J. B. S., 1927 A mathematical theory of natural and Punnett, R. C., 1923a Heredity in Poultry. Macmillan, London. artificial selection, Part IV. Proc. Camb. Philos. Soc. 23: 607– Punnett, R. C., 1923b Linkage in the sweet-pea (Lathyrus odor- 615. Reprinted in Weiss and Ballonoff (1975), pp. 98–106. atus). J. Genet. 13: 101–123. Hutchinson, G. E., 1979 The Kindly Fruits of the : Recollections Punnett, R. C., 1926 William Bateson. Edinb. Rev. 244: 71–86. of an Embryo Ecologist. Yale University Press, New Haven, CT. Punnett, R. C., ed., 1928 Scientific Papers of William Bateson, Vols. Koszul, R., M. Meselson, K. Van Doninck, J. Vandenhaute, and D. 1 and 2. Cambridge University Press, Cambridge/London/New Zickler, 2012 The centenary of Janssens’s chiasmatype theory. York. Genetics 191: 309–317. Punnett, R. C., 1930a Genetics, mathematics and natural selec- Lock, R. H., 1906 Recent Progress in the Study of Variation, Hered- tion: Review of Fisher (1930a). Nature 126: 595–597. ity, and Evolution. Murray, London. Punnett, R. C., 1930b See Fisher (1930b). Mazumdar, P. M. H., 1992 Eugenics, Human Genetics, and Human Punnett, R. C., 1950 Early days of genetics. Heredity 4: 1–10. Failings. Routledge, London. Punnett, R. C., 1952 William Bateson and Mendel’s Principles of Morgan, T. H., 1911 Random segregation vs. coupling in Mende- Heredity. Notes Rec. R. Soc. Lond. 9: 336–347. lian inheritance. Science 34: 384. Richmond, M. L., 2001 Women in the early history of genetics. Morgan, T. H., 1928 The Theory of the Gene, revised edition. Yale Isis 92: 55–90. University Press, New Haven, CT. Richmond, M. L., 2006 The domestication of heredity: the famil- Morgan, T. H., 1929 Bateson and Mendelism. Review of Punnett ial organisation of geneticists at Cambridge University, 1895– (1928). Nature 124: 171–172. 1910. J. Hist. Biol. 39: 565–605. Morgan, T. H., and C. J. Lynch, 1912 The linkage of two factors in Sturtevant, A. H., 1965 A History of Genetics. Cold Spring Harbor Drosophila that are not sex-linked. Biol. Bull. 23: 174–182. Laboratory Press, Cold Spring Harbor, NY. (Cold Spring Harbor Needham, J., 1967 Reginald Crundall Punnett. The Caian, Octo- Laboratory Press/Electronic Scholarly Publishing Edition, ber 1967, pp. 43–44. 2000.) Norton, H. T. J., 1928 Natural selection and Mendelian variation. Weiss, K. M., and P. A. Ballonoff, 1975 Demographic Genetics Proc. Lond. Math. Soc. 28: 1–45. Reprinted in part in Weiss and (Benchmark Papers in Genetics 3). Dowden, Hutchinson and Ballonoff (1975). pp. 107–131. Ross, Stroudsburg, Pennsylvania. Norton, B., and E. S. Pearson, 1976 A note on the background to Weldon, W. F. R., 1902 Mendel’s laws of alternative inheritance and refereeing of R. A. Fisher’s 1918 paper ‘The correlation in peas. Biometrika 1: 228–254. between relatives on the supposition of Mendelian inheritance’. Whitehouse, H. L. K., 1965 Towards an Understanding of the Notes Rec. R. Soc. Lond. 31: 151–162. Mechanism of Heredity. Arnold, London.

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