94 THE EVOLUTION THEORY 



Wasmann informs us that the parasitic larvae grow up just at the 

 time at which the ants are rearing their workers, and it is these, 

 therefore, which fall victims to the Lomechusa-larvae, and the result 

 is that a scarcity of young workers must soon make itself felt. The 

 workers seek to make this good by rearing as workers all the larvae 

 previously destined for queens. But this only succeeds partially, 

 because the development towards true females has already begun ; 

 thus mixed forms arise. 



This explanation would be rather in the air if we did not 

 know that, among bees, such changes in the manner of rearing are by 

 no means uncommon. Indeed they occur regularly when the queen 

 of a hive perishes and no more ' female ' eggs are in store ; young 

 worker larvae are then fed with royal food, and these develop into 

 queens. There can thus be no doubt that these insects have it in 

 their power to liberate to activity either the female ids or the worker 

 ids by a specific mode of feeding, and there is nothing contrary to 

 reason in admitting the possibility of an alternation of this influence in 

 the course of development, for something analogous occurs in regard 

 to secondary sexual characters, as, for instance, the appearance of 

 male decorative colours in ducks that have become sterile. 



But this change in the mode of rearing bee-larva3 gives rise to 

 pure queens and not to mixed forms, and we must therefore regard it 

 as undecided whether Wasmann's explanation is correct in this case, 

 and whether an abnormality in the constitution of the germ-plasm 

 may not be the true cause of this or other kinds of mixed forms 

 among ants. In any case the ' Lomechusa hypothesis ' rests upon the 

 assumption of different kinds of ids in the germ-plasm, as Pater 

 Wasmann expressly states, and the differences between the worker and 

 queen-ants have their cause in this, and not directly in the kind of 

 larval food. 



If there were not different ids corresponding to the different 

 kinds of individuals in the germ-plasm a kind of polymorphism 

 might indeed have arisen in the colony through diffierences in 

 nutrition, but it could not have been of the kind we now see — that 

 is, a sharply defined differentiation of persons, in adaptation to their 

 different functions. This presupposes elements in the germ which 

 can vary slowly and consistently in a definite direction without 

 causing any change in the rest of the germ. 



This state of affairs gives to the phyletic evolution of the workers 

 a great theoretical significance, for it proves that positive as well as 

 negative variations of the most diverse parts of the body, that simul- 

 taneous and correlative variations of many parts, can take place in the 



