SUMMAKY OF CURRENT RESEARCHES 



RELATING TO 



ZOOLOGY AND BOTANY 



(PEINCIPALLY INVERTEBEATA AND CRYPTOaAMIA), 



MICROSCOPY, Etc.* 



ZOOLOGY. 



VERTEBEATA. 

 a. Embryology, f 



Determination of Sex. J — L. Doncaster has discussed the more 

 important lines of evidence which bear on the problem of sex determina- 

 tion. Sex, although it is almost universally found, cannot be said with 

 certainty to be a necessary attribute of living things, and its real nature 

 remains an apparently impenetrable mystery. In the rare cases where 

 it seems to have disappeared, the organism thrives to all appearance just 

 as well without it. Perhaps the nearest approach to the deeper problems 

 of sex is through the study of its determination. 



The problems involved are concerned with existence of two distinct 

 sexes and the causes which determine whether an egg will develop into 

 a male or into a female, the comparative regularity with which they are 

 produced, and the developmeut of secondary sexual characters. 



In fertilization we get almost our only definite indication of the 

 ultimate nature and function of sex, for it implies the equal mingling 

 in every individual of sets of inherited characters derived from two 

 parents. Yet the two parents might have been similar and the sex- 

 elements similar, somewhat after the fashion seen in Paramecium and the 

 like. There is some advantage in the specialization of ova and sperma- 

 tozoa along different lines, and this is associated with sex differences. 

 But it is not certain whether the sex differences follow from a primary 

 division into egg-producing and sperm-producing individuals, or whether 

 the differences themselves are really primary, and lead to egg-production 



* The Society are not intended to be denoted by the editorial " we," and they 

 do not hold themselves responsible for the views of the authors of the papers 

 noted, nor for any claim to novelty or otherwise made by them. The object of 

 this part of the Journal is to present a summary of the papers as actually pub- 

 lished, and to describe and illustrate Instruments, Apparatus, etc., which are 

 either new or have not been previously described in this country. 



t This section includes not only papers relating to Embryology properly so- 

 called, but also those dealing with Evolution, Development, Reproduction, and 

 allied subjects. 



t The Determination of Sex. Cambridge (1914) 172 pp. (23 pis.). 



K 2 



