Alfred Russel Wallace, LL. D. 9 



of Organisms. XIII. The Geological Evidence of Evolution. 

 XIV." Fundamental Problems in Relation to Variation and 

 Heredity. XV. Darwinism as applied to Man. XVL Criti- 

 cisms. "XVII. Forces other than Natural Selection. 



The scope of Darwinism is wider than that of any of 

 Wallace's previous books, and he gives attention to the 

 voluminous literature which had grown up during the in- 

 terval which had elapsed since his first general synopsis 

 published in 1870. The most important part of the book 

 is the large portion which is devoted to the nature and uses 

 of colors in animals and plants. In this field "Wallace's 

 original contributions both to fact and theory are very in- 

 teresting and valuable. His chapter on the geological (i. e., 

 paleontological) evidence of evolution was hardly up to 

 the times, as the American work had not sufficiently at- 

 tracted his attention at the time of his writing. In his 

 criticisms of Spencer, Cope, Semper, and Geddes he denies 

 the efficacy of the Lamarckian factors use and disuse, and 

 the direct effect of the environment on organic structure, 

 but accounts for all variations in the latter by natural selec- 

 tion. Thus Cope had endeavored to explain the origin of 

 the divergence of the diplarthrous ungulate mammalia by 

 supposing that the even- toed line (Artiodactyla) were pro- 

 duced by walking in muddy ground, which spreads the toes 

 equally in all directions, while the odd-toed (Perissodactyla) 

 have descended from forms that walked on dry ground, so 

 that the stimulus of impact and strain was felt by the long- 

 est toe, which was accordingly developed at the expense of 

 the others, thus producing the horse. Dr. Wallace says 

 that such an explanation is not proved, and is unnecessary, 

 since it is evident that it was only necessary for variation 

 in these two directions to have appeared to have been at 

 once taken advantage of by natural selection. The odd- 

 toed type, being best adapted for progress on hard ground, 

 would survive, and the even- toed be eliminated ; while the 

 reverse process would take place among the types that in- 

 habited soft places. To the general proposition involved 

 in this explanation I will return ; but will only say now, in 

 passing, that Dr. Wallace does not thus explain the origin 

 of the" two variations in question ; nor is it certain that, 

 having once originated, the even-toed is not quite as effect- 

 ive as the odd-toed for rapid progress on hard ground. 



In his Chapter XV, Wallace again expresses his dissatis- 

 faction with natural selection as an explanation of the 



