4 The Scope and JPrmcljjles 



was explicitly admitted by Darwin, though that fact is 

 often ignored by his critics, and has been emphasized by 

 Mr. Spencer in his " Factors of Organic Evolution," as 

 well as by Prof. Cope, Dr. Eaymond, and the American 

 School of Evolutionists generally. " There is now much 

 reason," Mr. Wallace declares, "to believe that the sup- 

 posed inheritance of acquired modifications that is, of 

 the effects of use and disuse, or of the direct influence of 

 the environment is not a fact, and if so, the very foun- 

 dation is taken away from the whole class of objections on 

 which such stress is now laid." Such effects, for exam- 

 ple, as the diminished jaw in civilized man, and the dimi- 

 nution of the muscles used in closing the jaw in case of 

 pet dogs which are fed on soft food, are wholly accounted 

 for by the simple fact of the withdrawal of natural selec- 

 tion in keeping up the parts in question to their full 

 dimensions, in connection with Mr, Galton's law of "Re- 

 gression toward Mediocrity," whereby, it has been been 

 proved experimentally, there is a tendency of organs which 

 have been increased by natural selection, to revert to a 

 mean or average size, whenever the stress of circumstances 

 which compelled the operation of this law is removed. 

 Investigating the supposed effects of use and disuse in 

 wild animals, Mr. Wallace notes the circumstance that 

 " the very fact of use, in a wild state, implies utilitij, and 

 utility is the constant subject for the action of natviral 

 .selection; while among domestic animals those parts which 

 are exceptionally used are so used in the service of man, 

 and thus become the subjects of artificial selection." 

 " There are no cases among wild animals," he says, " which 

 may not be better explained by variation and natural selec- 

 tion," than by the law of use or disuse. He quotes Gal- 

 ton, and Prof. Weismann in his recently published " Essays 

 on Heredity," two of the most careful students of tliis 

 subject, in support of the non-heredity of acquired 

 variations ; and on the whole makes an exceedingly strong 

 argument in favor of natural selection as the great and 

 controlling factor in organic evolution. Prof. Cope and the 

 American evolutionists, he says, "have introduced theoret- 

 ical conceptions which have not yet been tested by experi- 

 ments or facts, as well as metaphysical conceptions which 

 are incapable of proof. And when they come to illustrate 

 these views by an appeal J;o palaeontology or morphology. 



