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Genetic Variability" Which Is Important to Our Understanding of the Chapters I to 5, Is an Account of Classical Cytogenetic

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Genetic Variability REVIEWS '5' genetic variability" which is important to our understanding of the behavioural being studied, it seems to many of us that it is only through such analyses, firmly based on a Mendelian model and designed not to obscure but to reveal, that the elucidation of gene action can be achieved. By avoiding such a formulation, Ginsburg may give the reader unacquainted with the existence of such techniques an unnecessarily pessimistic impression of the contribution which modern genetics, and especially biometrical genetics, can make to the study of human personality. P. L. Broadhurst. GENETICALPRINCIPLES AND PLANT BREEDING. Watkin Williams. Blackwell Scientific Publications, Oxford. 1964. Pp. x+504. 70s. GeneticalPrinciples and Plant Breeding is the latest addition to the compre- hensive series of textbooks on specialised fields of genetics which have been published by Blackwell Scientific Publications during the last few years. It is written for biology students, particularly those specialising in agriculture, and it is designed to cover their requirements from undergraduate to the completion of postgraduate training. It assumes only a slight aquaintance with Cytogenetics. Like the other books in this series the opening section, comprising Chapters i to 5, is an account of classical cytogenetics appropriately illustrated in this case by examples from flowering plants. The introductory chapter takes the form of an extended glossary of genetical terms and concepts covering gene action and interaction and qualitative and quantitative variation. The following chapters give accounts of the chromo- some theory of inheritance, linkage and recombination, numerical and structural changes in the chromosome complement and mutation and mutagens. The section ends with a clear, concise account of cytoplasmic inheritance and related phenomena in higher plants. The second section, Chapters 6 to 8, is concerned with the various aspects of sex determination, incompatibility systems and breeding systems which are found in higher plants and their significance for plant improvement. Adaptation and selection are the subjects of the third section, which consists of Chapters 9 to i i. It includes discussions of population structure, geographical distribution, speciation, response to domestication, selection for continuously varying characters, the role of selection in plant breeding and host parasite relationships and their bearing on breeding for disease resistance. The last chapter is devoted to special techniques in plant breeding and genetics. These include chromosome manipulation, induction of mutations and artificial aids to successful outcrossing. Genetical Principles and Plant Breeding clearly contains a unique combination of the pure and applied genetics of flowering plants. On the whole, the treatments of the various subjects covered in this book more than meet the requirements of the students to whom they are addressed. There is, however, one notable exception. No serious attempt is made to describe the aims, analytical techniques and conclusions of biometrical (or quantitative) genetics which is, after all, not only one of the most active fields in plant genetics, but the only approach to a genetical analysis of quantitative variation that is generally applicable to flowering plants. Where biometrical 152 REVIEWS formul are quoted, for example, those used for predicting the response to selection and the effect of inbreeding on the generation mean, they are introduced with only superficial explanation, derivation and justification. Furthermore, in one of the few discussions of the application of biometrical genetics to plant breeding, namely diallel analysis, the procedures are illustrated by one of the least satisfactory examples, for demonstrating its usefulness and power, that can be found in the literature. It is perhaps not surprising, therefore, that the author concludes that the analysis "may not offer much additional precision in return for the considerable computations involved ".Thiscan hardly be regarded as a fair summary of the assessment of the role of diallel analysis in plant genetics which has been made by professional plant breeders. Fortunately, the author gives extensive refer- ences to papers where more balanced and comprehensive assessments of the role of diallel analysis, and of biometrical genetics in general, can be found. J. L. JINK5. ELEMENTSOF CYTOLOGY. N. S. Cohn. Harcourt, Brace and World Inc. 1964. Pp. 368. $8.95. Tothose actively engaged in the study of the cell it has long been apparent that most of the fundamental problems of biology will have to be answered in terms of cell activities. For, what is fundamental to the cell is frequently fundamental to the individual, the population and the species though this proposition cannot be so often or so simply inverted. Despite this, the teaching of biology has not, traditionally, been founded on cytological principles. Indeed, as a student I was taught cytology as an appendix—a sweetmeat offered to take away some of the unpalatability of the main course. And the cytology that was then offered was little more than a description of certain cell components—of unknown function— crowned by an account—which I now know was inadequate—of mitosis and meiosis. Today, however, there is no longer any excuse for failing to recognise the importance, and to teach adequately the functional relationship, of these components. Neither is there any excuse for failing to relate these activities to development, to heredity and to evolution. Indeed a number of texts have already appeared with just these ends in view and the book under review is yet a further venture in this direction. Writing a book of this scope is not without difficulty. This stems principally from the fact that specialisation is no longer the prerogative of cell components—it applies equally to those who study them. For this reason it is becoming increasingly more difficult for one man to deal with all the various structures and their varied activities. And this, as I see it, is the great shortcoming of Cohn's book which frequently solves problems by ignoring them. As a result it is, in places, a mere skeleton of the truth. Personal experience would be needed to add the flesh, and the blood required to transform it into a whole. And constructing and even articulating a skeleton is not enough. It must be made to live. The book falls naturally and nicely into three parts—The Cytoplasm, The Nucleus and Nucleocytoplasmic Relations. There is little doubt, however, that much of the author's acquaintanceship with the nucleus, at least, is second-hand. Thus, sister-chromatids at mitotic metaphase are.
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