100 THE EVOLUTION THEORY 



tiation of the sterile workers into several castes, in the following 

 interesting manner. 



The task of the workers is to procure all the food necessary for 

 all the individuals of the colony in quantity and quality corresponding 

 to the demand ; failing this the whole colony would perish. Now the 

 different persons of the colony need different food, according to their 

 constitution and their functions. Soldiers, for instance, are more 

 powerful than ordinary workers, since they are adapted for fighting, 

 and they therefore require a different kind of food from the 

 weaker workers who are adapted only for other duties. Since the 

 soldiers have evolved from the latter by selection, what we may, for 

 the sake of brevity, call the soldier-food in the common stores of the 

 ants would be drawn upon more lavishly than before, and would 

 therefore disappear more quickly, and, whenever this occurred, those 

 workers which had already brought in this kind of food would be 

 impelled to bring more and more to satisfy the demand for it. But in 

 order to do this they would require to exert themselves more, and would 

 therefore require a larger quantity of food — not of course soldier- food, 

 but the particular kind which their particular qualities demanded. 

 Probably this second importation of food was undertaken by a second 

 kind of worker, for, according to Zehnder, each worker does not carry 

 all the kinds of food ; they are divided into legions, each of which has 

 its particular task of food-collecting to fulfil. 



In the end the storehouse of the ant-colony must contain 

 a provision in which the different kinds of food are in exact proportion 

 to the necessities of the different kinds of persons in the colony. It 

 must alter in its composition again as soon as, in the course of time, 

 one or other kind of person acquires new characters, for these presup- 

 pose a new kind of diet 



But how are these acquired characters to be transmitted since 

 neither soldiers nor workers reproduce ? Zehnder answers this by 

 pointing out that the sexual animals eat all the kinds of nourishment 

 which are accumulated in the stores, that is to say, all the different 

 kinds of food exactly in the proportion in which they have been 

 imported — the proportion in which the difierent kinds of persons are 

 represented in the colony. Thus the kinds of nourishment which 

 caused the appearance of the newly acquired characters in the non- 

 sexual animals also reached the sexual animals and their sex-cells, 

 and there gave rise to substances which evoke the relevant qualities 

 in their descendants, for instance, in the soldiers, or in the still more 

 modified workers, and so on ; and thus we have an ' inheritance of 

 acquired characters.' 



