THE CANADIAN ENTOMOLOGIST. 177 



A number of ''extreme variates" are noted, which the author declines 

 to call mutants, but in later discussions refers to as " mutants." It seems 

 to me the quotation marks might well have been left off. The author 

 maintains " that ' mutation ' is not a special kind of variability different 

 from that of ' ordinary fluctuating variation,' but it is a part of the normal 

 variability, and the direct response of the germ plasm to stimuli." If I 

 understand the case correctly, these "extreme variates" are quite extreme; 

 they are rare, occurring only once in 6,000 cases ; and breed triie^ a thing 

 which ordinary variates do not do. This is my idea of a mutant. The 

 mere question of terms, however, is relatively unimportant. The fact is, 

 Tower has given us one of the strongest arguments for the importance of 

 mutations that has ever been presented, although he seems to think 

 otherwise. He says: "The breeding 'mutants' in our gardens and 

 laboratories can not tell us how they would succeed in nature ; my 

 experience with these beetles is that they fare badly, and, as far as I can 

 discover, that they play a minor role in the evolution of species." How- 

 ever, he had already stated (p. 273 et seq.) that not only did pallida, one 

 of the " mutants," breed absolutely true for six generations in the 

 laboratory with " no tendency to revert to the parental species " 

 (decemlifieata), but that from 14 males and 15 females allowed to shift for 

 themselves in nature, 1,580 /(^///</« offspring of the 6th generation were 

 found, and he " felt that further experiment with this form unconfined in 

 nature was' neither safe nor desirable, and exterminated the entire lot." 

 It is true that 2<^ pallida is more than he ever found in na'^ure at one time 

 and place, but he did find 6 at Clifton, Ohio, and he notc^ that occasion- 

 ally, as at Cabin John Bridge, Md., in 1900, sports are relatively very 

 abundant. /"a/Z/V/a is only one of a number of similar cases that Tower 

 found. If I had been so fortunate as to obtain his results I would have 

 drawn quite the opposite conclusions, and would have supported the 

 mutation theory most loyally, believing it to be the statement of one, at 

 least, method of evolution. 



But the cream of Tower's paper has not yet been noted. After 

 discussing (Chap. Ill) the ontogeny, chemistry, etc., of coloration in 

 Leptinotarsa, and showing that marked colour variations can be brought 

 about by varying the environmental conditions during development, but that 

 these variations are fiot inherited ; and after treating of habits, assnrtative 

 mating, etc., in Chapter IV, he shows in Chapter V how inheritable 

 variatiofis can be brought about artificially. Selection alone is apparently 



