76 DARWINISM TO-DAY. 



by the process of natural selection. But PfefTer, who is 

 an ingenious debater, makes out a very plausible case for his 

 contention. 



Of the many special questions that have been asked of the 

 selectionists two may be mentioned, simply as examples illus- 

 trative of a rather formidable category of objections most 

 of which are concerned with certain particular phases of 

 evolution or groups of evolution phenomena rather than 

 with the whole problem of species-forming. Many such 

 special objections or questions touching specific cases were 

 taken up and answered by Darwin in his "Origin of 

 Species." Morgan has recently ("Evolution and Adapta- 

 tion") gone over critically many of these special objections 

 and Darwin's answers to them, and pointed out clearly 

 that in numerous cases Darwin relied for his answers on 

 evolution factors which the neo-Darwinians have attempted 

 to read out of court. In many tight places Darwin availed 

 himself of the Lamarckian factor of the cumulation, through 

 inheritance, of the effects of use and disuse, or of other 

 functional stimuli originating either in internal or ex- 

 trinsic conditions. That is, Darwin, while constantly trying 

 to rely, and whenever possible relying on natural selection 

 as the species-forming and adaptation-explaining cause, 

 never hesitated, when it seemed necessary, to admit the 

 influence and effect of the inheritance of acquired characters 

 or the influence of other, to him, unknown factors. In 

 most cases of degeneration, for example, he adopted a 

 Lamarckian explanation. 



The question of how sterility between species could have 



arisen is a case in point. "That this property of species is 



useful to them in the somewhat unusual sense 



expiSg 7 inter- that it keeps them from freely mingling with 



species sterility other species is true," says Morgan; "but this 



by selection, 



would be a rather peculiar kind of adaptation. 

 If, however, it be claimed that this property is useful to 



