SUMMARY OF CURRENT RESEARCHES 



RELATING TO 



ZOOLOGY AND BOTANY 



(PKINCIPALLY INVEKTEBEATA AND CRYPTOGAJIIA), 



MICROSCOPY, Etc.* 



ZOOLOGY. 



VERTEBRATA. 

 a. Embryologry.t 



Proportion of Sexes produced by Whites and Coloured People 

 in Cuba4 — Walter Heape notes that strong evidence has been brought 

 to show that individual spermatozoa and ova have definite sexuality. 

 It has been suggested that the sex of the offspring must be determined 

 by either ovum or spermatozoon, not by both, and it has been claimed 

 that a male ovum must be fertilised by a female spermatozoon, and, 

 vice versa, a female ovum by a male spermatozoon. So far as the 

 evidence now goes, it would seem possible that in some animals the sex 

 of the offspring is determined by the spermatozoon, and in other 

 animals by the ovum. As regards Mammals, the evidence available is 

 in favour of the view that the ovum determines the sex of the offspring. 



A female Mammal produces only a limited number of her ovarian 

 ova ; others degenerate and are absorbed ; there is a struggle for 

 existence and a process of selection going on in the mammalian ovary. 

 Just as female larva? require more nourishment and more favourable 

 conditions than do male larva?, so the selection of male or female 

 ovarian ova, for production, is liable to be influenced by the food 

 supplied to the ovary by the mother, and therefore by the conditions of 

 metabolic activity she experiences. 



Variations in the proportions of the sexes may be referable to those 

 extraneous forces which act as selective agents on the ovarian ova. In 

 this connection Heape studied the proportion of the sexes produced by 

 whites and coloured peoples in Cuba. The whites produce a larger 

 proportion of males than the coloured people. In illegitimate births 



* 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. 



\ Proc. Roy. Soc, Series B, lxsxi. (1909) No. B 545, pp. 32-7. 



