Chromosome Numbers in Cimex Such a Suggestion Is As Useless As Mather's

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358 NATURE AUGUST 20, 1938, VoL. 142 differ profoundly according to the intensity of of which can be performed by the remainder of the Feulgen's reaction. The proximal ends of the auto• complement, or are genetically inert. somes continue to unite with the heterochromatin All C. lectularius material so far examined has region of the X -chromosome in the same way as yielded a haploid autosome count of twenty. Since they united formerly with the chromocentre. these three karyotypes form a series having chromo• When the chromosome bands begin to form, the some numbers which are multiples of four, there is heterochromatin region extends still more and the to suppose that (a) the genus is polyploid in small number of chromomeres of early stages dis• ortgm, (b) the stem number in Cimex is four and not integrate lengthwise into a greater number. When six as was suggested by Slack1 and Vandel2 for the the genonemata become double, the number of Heteroptera. H. D. SLACK. chromomeres in the row is also doubled in both University, euchromatin and heterochromatin chromosome Glasgow. regions. Thm; a typical picture of the inert region of June 28. the X-chromosome of D. funebris in the salivary 1 Slack, H. D., British Association, Nottingham (1937) (nnpnblished). gland nuclei of large larvm is obtained. 'Vande!, A., Proc. Zoo!. Soc., A, 107, 519 (1937). When the bands in the salivary gland chromosomes of D. melprophase as seen in salivary glands would 'Heitz, Z. ZeUJ. u. micr. Anat., 19 (1933). account for the behaviour of the heterozygote of the Delta 49 inversion, but without factual evidence Chromosome Numbers in Cimex such a suggestion is as useless as Mather's. It is A SUB-SPECIES of Cimex, phenotypically inter• possible that Mather is correct in his assumption mediate between C. lectularius and C. columbarius regarding this theory, but more genetical evidence is and obtained from laboratory white rats, has been required before acceptance is possible. found to comprise two forms differing in the number F. w. SANSOME. of chromosomes. In most cases the haploid number Botanical Department, of autosomes is twenty-four, but in occasional University of Manchester, specimens it is sixteen. No variation in phenotype, Manchester, 13. correlated with thi.,; change in number, has been July 25. observed, nor is the normal course of meiosis affected. 1 Mather, K., NATURE, 142, 157-158 (1938). This suggests that eight autosomes in this sub• • Charles, D. R., J. Genet, 36, 103-26 (1938). either represent a duplicate set the functions 3 Mather, K., J. Genet., 33, 207-35 (1936).