60 Bulletin American Museum of Natural History. [Vol. XXIII^ 



intermediate forms of workers must have its special set of 'determinants,'" 

 causing its special set of modifications of organs; for he cannot assume that 

 while perfect females and the extreme types of workers have their different 

 sets of determinants, the intermediate types of workers have not. Hence^ 

 we are introduced to the strange conclusion that besides the markedly 

 distinguished sets of determinants there must be to produce these interme- 

 diate forms, many other sets slightly distinguished from one another — a. 

 score or more kinds of germ-plasm in addition to the four chief kinds [namely 

 for the male, female, soldier, and worker]. Next comes an introduction to 

 the still stranger conclusion, that these numerous kinds of germ-plasm^ 

 producing these numerous intermediate forms, are not simply needless but 

 injurious — produce forms not well fitted for either of the functions dis- 

 charged by the extreme forms : the implication being that natural selection 

 has originated these disadvantageous forms ! If to escape from this necessity 

 for suicide Professor Weismann accepts the inference that the differences 

 among these numerous intermediate forms are caused by arrested feeding 

 of the larvae at different stages, then he is bound to admit that the differences- 

 between the extreme forms, and between these and perfect females, are 

 similarly caused. But if he does this, what becomes of his hypothesis that 

 the several castes are constitutionally distinct, and result from the operation 

 of natural selection ? Observe too that his theory does not even allow him 

 to make this choice; for we have clear proof that unlikenesses among the 

 forms of the same species cannot be determined this way or that way by 

 differences of nutrition. English greyhounds and Scotch greyhounds do 

 not differ from one another so much as do the Amazon-workers [soldiers] 

 from the inferior workers, or the workers from the queens. But no matter 

 how a pregnant Scotch greyhound is fed, or her pups after they are born, 

 they cannot be changed into English greyhounds: the different germ-plasms 

 assert themselves spite of all treatment. But in these social insects the 

 different structures of queens and workers are determinable by differences, 

 of feeding. Therefore the production of their various castes does not 

 result from the natural selection of varying germ-plasm." 



If we omit the portion of Spencer's argument in which he postulates the 

 dysteleological character of the intermediates, or desmergates, as I have 

 called them — a probably erroneous assumption, since there is every reason 

 to believe that individuals embodying varying combinations of the worker 

 and soldier traits may be just as useful to the colony as the soldiers and 

 workers themselves — the position taken in the above quotation seems to be 

 unassailable. But when Spencer comes to deal with the cr\icial problem, 

 namely the marvelous, purposeful coadaptation of organs in the sterile 

 workers, he fails as signally as Weismann, for no one familiar with the habits. 



