Manchester Memoirs, Vol. I. (1906), No. 0- 25 



he champions, with a certain amount of success one must 

 admit. But it certainly appears to be pushing the matter 

 beyond reasonable limits when Boveri and other investi- 

 gators suggest that different sized chromosomes may 

 bear different or correlated characters. 



The cytoplasm of the ovum and the spermatozoon is 

 left out of the question entirely in questions of heredity 

 by these investigators. This is an unjustifiable pro- 

 ceeding. The cytoplasm of the spermatozoon is in a 

 highly concentrated condition, as also is the nucleu.s, and 

 v/e have no evidence against the view that the cytoplasm 

 of both ovum and spermatozoon or of either of them may 

 bear some hereditary characters as well as the nucleo- 

 plasm. It must be remembered also, as will be shown 

 later, that in some ova a large quantity of nucleoplasm is 

 scattered in the cytoplasm. Until it has been proved 

 that the cytoplasm takes no part whatever in the trans- 

 ference of hereditary characters, all hypotheses which 

 only take the chromosomes into account, must be received 

 with due caution. 



In those parthenogenetic eggs of insects in which 

 there is a reduction in the number of chromosomes, it is 

 probable that the normal number is formed later as a 

 physiological necessity. I believe, with Delage, that the 

 cell is able to re-establish the normal number of chromo- 

 somes, and that ' si le nombre des chromosomes est 

 constant chez les animaux, ce n'est pas, comme on le 

 croit, parceque ces organites ont une personalite qui les 

 rend individuellement permanents, c'est parceque ce 

 nombre est une propriete specifique de la cellule, une 

 constante de la cellule.' This raises the question as to 

 whether a fixed number of chromosomes always occurs. 

 It is usually considered that this is the rule, but certain 

 observers have found that this is not always the case. 



