80 Bulletin American Museum of Natural History. [Yo\. XXIIl, 



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 dis- 

 tinct worker and soldier castes. It thus becomes impossible even in closely 

 related species of certain genera, like Pheidole, to predict the characters of the 

 worker from a study of the cospecific soldier or vice versd. And while adap- 

 tive characters in stature, sculpture, pilosity and color must depend for their 

 ontogenetic development on the nourishment of the larvae, it is equally cer- 

 tain that they have been acquired and fixed during the phylogeny of the 

 species. In other words, nourishment, temperature, and other environ- 

 mental 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 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. 

 Far preferable appears to be the view of the constantly increasing number 

 of biologists who conceive the adult characters to be represented in the germ 

 as dynamic potencies or tensions rather than as morphological or chemical 

 determinants. 



Having touched upon this broader problem of heredity it will be nec- 

 essary 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 somatogenic traits. 

 In establishing this view and the all-sufficiency of natural selection to which 

 it leads, W^eismann seems to me 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 nevertheless 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 often overlooked. 

 Marchal (vide ante, p. 65), has shown how readily the workers of the social 

 wasps assume this state, and the same is true of 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 pres- 

 ent 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 (l. c), and fertile workers by Silvestri (/. c). Among ants 

 fertile, or gynsecoid, workers occur so frequently as to lead to the belief 

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



