376 THE GERM-PLASM 



minants are present in the yellow variety also. If we imagine 

 that the two sexes were identical as regards the wing-marking 

 in the immediate ancestors of Papilio turmis, as they are in the 

 closely allied European species Papilio machaon^ and that this 

 monomorphic ancestral form had persisted — in California, let 

 us say, — we should have an instance of that kind of poly- 

 morphism which Wallace has described in the case of Papilio 

 meinnon^ in which there are one male and three female forms. 

 In this case we must suppose that the first and oldest form 

 possessed j/V/^/^-determinants for the wings ; while in the 

 second and third forms the determinants were double, and their 

 ' male ' halves retained their original nature, the female halves 

 becoming modified in two different directions. 



It is therefore not necessary, as might have been supposed, 

 to assume the existence of triple determinants from the fact of 

 the trimorphism of a species alone, or of quadruple or quintuple 

 ones in the case of polymorphism. 



The polyniorpJiisni of animal and plant stocks rests on a 

 different basis, as it concerns the physiologically dissimilar 

 members of a higher stage of individuality — that of the stock. 

 This kind of polymorphism has already been treated of as a 

 phenomenon of development in connection with alternation of 

 generations. We must, however, take the closely allied poly- 

 morphism of animal cojnmunities into consideration. 



The differences between the male and female individuals in 

 bees has already been referred to the existence of double- 

 determinants. But a third form of individual, the worker, 

 occurs in the honey-bees. These workers differ from the 

 females in the slight development of the ovaries, the ovarioles 

 not only being fewer in number than in the ' queen,' but even 

 frequently containing no eggs at all, and at most only very few. 

 The receptaculum seminis is also more or less reduced, and the 

 abdomen is much shorter and thinner than that of the queen 

 bee. If these were the only differences between the two forms, 

 there would scarcely be any need to assume the existence of 

 special determinants for these parts in the germ-plasm of the 

 workers : we might imagine that the determinants of the 

 ovarioles, for example, were so constituted as to become active 

 in consequence of abundant nourishment, and to cause the 

 development of ovarioles ; while a smaller supply of nutriment 

 would not always be sufficient for this purpose, and thus the 



