84 Heredity, 



gemraule may unite or conjugate in the ovum with 

 particles which are not perfectly equivalent to it, but 

 only very closely related to it. Thus a variation may 

 affect a considerable number of related cells at the same 

 time, or a variation in any part may cause in succeeding 

 generations tlie variation of homologous parts, thus pro- 

 ducing what Darwin has called correlated variation. "W'e 

 can also understand how it is that when any part of a 

 complicated organ varies, variations in other parts of it 

 are also soon presented for tlie action of natural selec- 

 tion, so that an harmonious readjustment is soon estab- 

 lished. 



According to this view we must believe that all the 

 characteristics v»'hich are established as true race- 

 characteristics, as hereditary peculiarities of the species, 

 are transmitted by the ovum, Avhich has in itself the 

 power to develop, when excited by a i:)roper stimulus 

 which may or may not be due to imjiregnation, into a 

 new individual of the parent form. 



New variations, on the other hand, are produced 

 throuQ-li the a<xencv of 2:emmules thrown off from cells 

 liice those in which the variation appears. 



Gemmules may penetrate to all j^arts of the body, and 

 they may thus give rise to bud-variation and to analogous 

 changes; or they may penetrate to an ovarian ovum 

 and give rise to variation without fertilization: but as 

 these phenomena depend upon chance, they are com- 

 paratively rare, while the aggregation of the gemmules 

 in the male cell and their transmission by impregnation 

 are normal processes. 



According to this view, the male element is the origi- 

 nating and the female the perpetuating factor; the 

 ovum is conservative; the male cell progressive. Hered- 

 ity or adherence to type is brought about by the ovum; 



