DETERMINATION OF SEX 



Experimental Biology Making Progress in the Solution of Fundamental Problem- 

 Sex-control in Men Now Impossible but May Some Day Be Realized. 



Review of a Book by Leonard Doncaster 

 Fellow of King's College, Cambridge, England 



HARDLY any problem in biology 

 has aroused such interest as 

 that of sex, and the amount 

 written on it is staggering — 

 the munber of hypotheses put forward 

 to explain the determination of sex 

 is said to be not far from 500. As 

 long as the problem was attacked only 

 by wordy speculation, based on philo- 

 sophical theories or observation of 

 uncontrolled phenomena, little progress 

 could be made; but the experimental 

 school of biology attacked it in a more 

 direct way, and is beginning, its adher- 

 ents think, to see light. "The last 

 few years have seen a considerable 

 advance, and we now know at least 

 something of the causes which lead to 

 the production of one or the other sex, 

 although of the manner in which these 

 causes act our ignorance is still pro- 

 found." 



The experiments of the biologists 

 are scattered through a volimiinous 

 periodical literature, and it is therefore 

 well worth while to have them brought 

 together and digested by a man who is 

 himself a leader in the work. Dr. 

 Leonard Doncaster, superintendent of 

 the musermi of zoology at Cambridge 

 University, has undertaken the task, 

 and his book, ^ "The Determination of 

 Sex," is not only up-to-date and critical, 

 but written in a clear and pleasing 

 style, which makes it a welcome addition 

 to genetic literature. At a time when 

 biologists tend to express their ideas 

 in mathematical symbols, there is need 

 for leaders of the science who are able 

 to expose their subjects in literary 

 English; and Dr. Doncaster proves 

 himself to be such a one. 



His review is also marked by an 

 unusually conservative attitude. "The 

 study of sex has not yet reached a stage 

 at which it is possible to give an account 

 of the established facts, and of generally 

 accepted inferences from them, which 

 shall be even comparatively free from 

 controversial matter," he remarks in his 

 preface. "The subject has been ap- 

 proached by many quite different lines, 

 and these lines, although convergent, 

 have as yet given no indisputable 

 indication of the central point towards 

 which they all tend." Nevertheless, 

 some solid facts seem well established, 

 and it may be of interest to review 

 these in company with Dr. Doncaster. 

 His book does not discuss sex-determina- 

 tion in plants, and a large part of his 

 illustrative material is drawn from 

 breeding experiments with insects — 

 work to which he himself has for a 

 munber of years given a large part of 

 his time. 



THE PURPOSE OF SEX 



In the first place, the author does not 

 subscribe to any one of the theories 

 which have been confidently put forward 

 to explain the origin of sex: — the reason 

 why the existence of two sexes is an 

 advantage to a species. " It is a remark- 

 able thing," he observes, "that apart 

 from the fundamental attributes of 

 living matter — assimilation, irritability, 

 growth, and so forth — no single char- 

 acter is so widely distributed as sex; 

 it occurs in some form in every large 

 group of plants and animals, from the 

 highest to the lowest, and yet of its 

 true nature and meaning we have 

 hardly a suspicion. Other widely dis- 



1 The Determination of Sex, by L. Doncaster, Sc. D. Pp. xii+172, Svo, 22 plates; glossary 

 and bibliography. Cambridge (England), University Press; New York, G. P. Putnam's Sons'; 

 1914. Price, $2 net. 



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