THE CHROMOSOMES IN RELATION TO 

 THE DETERMINATION OF SEX 1 



By EDMUND B. WILSON, Ph.D., D.Sc. 



Professor of Zoology, Columbia University ; New York 



Introduction 



As Mr. Doncaster has recently indicated in this journal, 2 the 

 view that sex is determined by conditions external to the germ 

 has in recent years slowly given way to the belief that it is 

 primarily established by an automatic mechanism within the 

 germ-cells. The change of front in regard to this time-honoured 

 and most interesting problem has been due to the convergence 

 of evidence from two widely different lines of inquiry, one 

 relating to the facts of sex-heredity, the other to the cytological 

 constitution of the germ-cells. It is the purpose of this review 

 to consider especially the second of these ; but the bearing of 

 the data will be more clearly apparent if an account of them 

 is prefaced by a brief mention of a few of the more important 

 facts derived from other sources. 



Though many of the earlier experiments seemed to show 

 that sex may be determined or influenced by conditions of 

 nutrition and the like, that act upon the fertilised egg or the 

 embryo during its development, this conclusion has received 

 little or no support from more recent investigation. It is true 

 that in the case of hermaphrodites — such as Hydra, or the 

 prothallia of ferns — the organs of one sex or the other may 

 be delayed in development, or altogether suppressed, by 

 particular conditions of the environment. It seems also clearly 

 to be proved that the change from parthenogenetic to sexual 

 development in dioecious forms (which involves the appearance 

 of males and of sexual females) may likewise be influenced 



1 The following review, prepared at the invitation of Prof. Farmer, follows 

 the same general lines as an address on the subject given by the author before 

 the American Association for the Advancement of Science at the Baltimore 

 meeting in December 1908, and printed in the issue of Scienceiox January 8, 1909. 

 The results of a number of important contributions to the subject, since published, 

 are here incorporated. 



2 Science Progress, July 1909, IV. pp. 90-104. 



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