8 THE SEX-COMPLEX 



Predetermi- that very little direct information can be obtained con- 

 x> cerning the human species. Most of the evidence has, 

 therefore, been derived from a study of the lower 

 animals. 



The general hypothesis stated under this heading may 

 be subdivided into the following alternatives : (a) That 

 sex is predetermined in the ovum (and possibly the 

 spermatozoon) from the earliest development of the ger- 

 minal cells, and that no alteration is possible ; (b) That, 

 while the sex may be said to be predetermined in this 

 way only for normal circumstances, altered conditions 

 of nutrition and environment may affect the gametes, 

 and thus influence the ultimate sex of the zygote. 



Dimorphism As to the unalterable primary determination of sex in 

 the gametes which is propounded in the first subdivision, 

 there is evidence that in some insects and in certain 

 snails the spermatozoa are dimorphic. For instance, 

 Henking 1 found that some of the spermatozoa in the 

 bug Pyrrhocoris possess an additional chromosome. 

 This has been supposed to be an example of bisexuality 

 in regard to the spermatozoa. According to Marshall 2 

 it is certain that the ova, also, have one more chromo- 

 some than the spermatozoa containing the lesser number. 

 It is believed that the conjunction of ova with sperms 

 having the greater number of chromosomes leads to 

 the production of females, and the fusion of ova with the 

 sperms having the lesser number to the development of 

 males. Other investigators have shown that differences 

 in the number of the chromosomes in the gametes are 

 found in many species of insects, and that even in the 

 fowl there are dimorphic spermatozoa. 



Beard 3 and other observers believe that the sex- 

 potentiality exists in the unfertilized ovum, and that 

 when there are two kinds of spermatozoon in the same 

 subject one variety is functionless. In this connexion 

 it may be pointed out that it is, of course, quite an old 



1 Henking, H., Zeitsch. /, Wiss. ZooL, 1890, vol. xlix, p. 503. 



2 Marshall, F. H. A., The Physiology of Reproduction, 1919, p, 623, 



3 Beard, J., ZooL Jahrb. 1902, vol. xvi, p. 703, 



