52 Riley — Presidential Address. 



the social insects offer the most serious obstacles to the accept- 

 ance of the theory of natural selection as an all-sufficient theory 

 to exjDlain the phenomena, yet the facts are perfectly explicable 

 upon the general principles that have governed the modification 

 of organisms, among which that of natural selection plays an im- 

 portant, but limited part. 



In the economy of the Hive Bee we have seen that all the 

 neuters are structurally alike, and that the different functions 

 which they perform result from inherited tendencies or structural 

 peculiarities developed at different ages. There are some records 

 of abnormal workers, small drones, and slight variatioiis in the 

 amount of arrestation of development; but on the whole the 

 three classes of queen, worker and drone are remarkably well 

 differentiated and fixed. We have seen that the differences in the 

 two former classes result from conditions of food, treatment and 

 environment of the young, and are under the control of the 

 colony. Each fertile Qgg has the potentiality of developing a 

 fertile queen, and as the neuters, under exceptional conditions, 

 are able to lay eggs which invariably produce drones, the queen, 

 through such drones, must occasionally inherit indirectly from 

 the workers. At bottom, however, the differentiation between 

 the workers and the queen is purely a matter of food and bring- 

 ing up, or education, as the French would more correctly call it. 

 In other words, the ultimate result is decided for each generation 

 in the treatment of the young or the larva?. The drone results 

 from an unfertilized Qgg, and as the Qgg is only fertilized when 

 the tip of the queen's abdomen is pressed into a worker cell, and 

 not when thrust into a drone cell, the production of drones is 

 also under control of the colony. 



I have already called attention to the fact that other species 



recognized by Darwin in framing his tentative theory of pangenesis. 



Weismanu's efforts to derive a physical theory of rej>roduction and evo- 

 lution hud a paralell in the efforts of those entomological histologists who, 

 starting with the conception that the development of the individual was 

 but an unfolding of structures already nascent in the embryo, expected to 

 find — and even claim to have found — ^all the structures of the imago repre- 

 sented, en petit, in the larva. In truth, however, there is a total re-adjustment 

 of cells, and development de novo of organs, with each im]>ortant change or 

 molt, and the vital force which impels this develojiment, whether of the 

 minutest bodily structure or the subtlest intellectual attribute, is the great 

 mystery beyond explanationt 



