STERILE INSECTS. 239 



tage to the individual, that a certain part be modi- 

 fied in any direction, we can understand how this 

 may be done by the selection of individuals with 

 favorable variations. The various organs do not 

 reproduce, and may be compared to the working 

 castes of insects. It is possible thus to look upon 

 the whole colony as an individual, the males and 

 females as the reproductive organs, and the workers 

 corresponding to other organs. If now it be of ad- 

 vantage to the colony that these working organs 

 should be differentiated into castes, the colonies 

 which presented favorable variations in this direc- 

 tion will be naturally selected, while those colonies 

 which do not have such variations will be extermi- 

 nated in the struggle for existence. Or, to put it in 

 other terms, the females which have, in times past, 

 produced young showing a tendency toward differ- 

 entiation into castes of workers, will have been able 

 to form colonies, while the females whose offspring 

 did not show this tendency toward differentiation 

 will not have been able to form colonies. Those 

 queen bees which did produce differentiated young, 

 and consequently did form colonies, would eventu- 

 ally give birth to other females, and these females 

 of the second generation will in turn have inherited 

 the same tendency from their parent. On the other 

 hand, bees which could not form colonies would not 

 have been able to produce other generations, and 

 would thus have become extinct. When, then, we 

 look upon the colony as an individual, and the 

 castes as organs, the difficulty is not insoluble. 

 This explanation is certainly very ingenious, and 



