Xo. .1T_>] MALE CRAYFISH 11777/ FEMALE OlUiAXS 471 



female producing. 4 We assume that every egg is fertil- 

 ized and will be male or female according to the sperm 

 that unites with its nucleus. But a gynandromorph 

 might arise by adding to the male or the female some 

 organs of the opposite sex due to the independent de- 

 velopment of the opposite kind of sperm in parts of the 

 egg. All sorts of gynandroniorplis might he imagined 

 upon this basis. Moreover, we might assume the abnor- 

 mal cases of duplication of sex organs in one individual, 

 such as studied by Bateson, to be due to the independent 

 development of sperms that happened to be of the same 

 kind as the one that fused with the egg nucleus. In 

 theory we might even refer the doubleness of organs not 

 concerned with sex to some sort of super fertilization. 



Whether such hypotheses have any value may be de- 

 termined by future experiments in the cross breeding 

 of crayfish. Such experiments may enable us to decide 

 whether gynandroniorplis arise before, during or after 

 fertilization and may throw light upon their causation. 

 The crayfishes in this part of the world, are especially 

 well adapted to these experiments, for if crosses can be 

 obtained at all, we may expect to distinguish between 

 pure and mixed sex organs, since both the male and the 

 female have external organs that are at the same time 

 essential sex organs and characteristic specific characters. 



Meanwhile the totality of facts known seems to mean 

 that the gynandromorph crayfishes are caused by un- 

 known disturbances, which may happen at various periods 

 of ontogeny, though probably more often in the ovarian 

 egg; that these disturbances may have no connection with 

 the gonads ; and that if in some cases the disturbances are 

 po.sihlva— iatedwith poivspermy, in general they seem 

 more fundamental and deep seated amidst the causes of 

 symmetrical form within the egg. 



