POLYMORPHISM. "5 



The foregoing observations indicate that in morphological charac- 

 ters the worker and female of the same species have advanced or 

 digressed in their phylogeny, remained stationary or retrograded, 

 independently of each other. The same peculiarity is also observable in 

 species with distinct worker and soldier castes. It thus becomes im- 

 possible, even in closely related species of certain genera, like Phci- 

 dole, to predict the characters of the worker from a study of the co- 

 specific soldier or rice versa. And while adaptive characters in sta- 

 ture, sculpture, pilosity and color must depend for their ontogenetic 

 development on the nourishment of the larvae, it is equally certain that 

 they have been acquired and fixed during the phylogeny of the species. 

 In other words, nourishment, temperature, and other environmental 

 factors merely furnish the conditions for the attainment of characters 

 predetermined by heredity. We are therefore compelled to agree with 

 Weismann that the characters that enable us to differentiate the castes 

 must be somehow represented in the egg. We may grant this, however, 

 without accepting his conception of representative units, a conception 

 which has been so often refuted that it is unnecessary to reconsider it in 

 this connection. 



Having touched on this broader problem of heredity it will be neces- 

 sary to say something about the inheritance or non-inheritance of 

 acquired characters, especially as Weismann and his followers regard 

 the social insects as demonstrating the non-transmissibility of somato- 

 genic traits. In establishing this view and the all-sufficiency of natural 

 selection to which it leads, Weismann seems to have slurred over the 

 facts. While he admits that the workers may lay eggs, and that these 

 may produce male offspring capable of fertilizing females, he never- 

 theless insists that this is altogether too infrequent to influence the 

 germ-plasm of the species. I venture to maintain, on the contrary, 

 that fertile workers occur much more frequently in all groups of social 

 insects than has been generally supposed. As this fertility is merely a 

 physiological state it has been overlooked. Marchal has shown how 

 readily the workers of the social wasps assume this state, and the 

 same is true of the honey-bees, especially of certain races like the 

 'Egyptians" and "Cyprians" (Apis mellifica-fasciata and cypria). 

 In the hives of these insects fertile workers are either always present 

 or make their appearance within a few days after the removal of the 

 queen. In the termites fertile soldiers have been observed by Grassi 

 and Sandias and fertile workers by Silvestri. Among ants fertile 

 or gynaecoid workers occur so frequently as to lead to the belief that 

 they must be present in all populous colonies. Their presence is also 

 proved by the production of considerable numbers of males in old 



