DARWINISM TO-DAY. 



not only are of no conceivable utility in the struggle for 

 -existence but are in many cases of obvious disadvantage. 

 It relies wholly on sexual selection to explain them, and 

 yet in Wolff's eyes, and indeed in the eyes of most biologists, 

 sexual selection is practically discredited. It certainly can- 

 not explain some or many of these characters. (See account 

 of the sexual selection theory and the criticisms of it in 

 the next chapter.) Therefore, say Wolff and other anti- 

 Darwinians, natural selection is undermined in just so far 

 as it relies on the sexual selection theory to sustain it. 



The other objection is that the natural selection theory 



rests altogether too largely on an unwarranted analogy with 



Natural selec- the phenomena of artificial selection. Plate 20 



tion rests too j las graphically expressed the contrast between 



largely on an 



analogy with arti- the facts and processes of the two kinds of 

 selection in the following double-column table : 



ficial selection. 



ARTIFICIAL SELECTION. 



(1) rests on the wish (IVillcn) 

 and intelligence of the breeder, 

 except in a certain few cases of 

 "unintentional breeding" (See 



Darwin, "Origin of Species.") 



(2) selects exceptional, most 

 widely divergent characters, 

 which appear only in a few 

 individuals. 



(3) complete isolation (pure 

 breeding) of the selected indi- 

 viduals. 



(4) often leads to exaggerated 

 development and to a sickly dis- 

 position, so that the whole con- 

 stitution suffers. 



(5) leads comparatively rapidly 

 to new forms. 



(6) The artificially-produced 



NATURAL SELECTION. 



(i) rests on the unvolitional 

 and unreasoning resultant of 

 natural forces. 



(2) is a selection of slight dif- 

 ferences, appearing simultane- 

 ously in many individuals. 



(3) pure breeding is often very 

 difficult through the possibility 

 of crossing with the parental 

 type. 



(4) effects no injury to the 

 whole constitution, but on the 

 contrary a strengthening and 

 bettering of it. 



(5) The modification of species 

 is effected, presumably almost 

 always, very slowly, for if it 

 were otherwise the appearance 

 of new species would be often 

 observed. 



(6) The natural races (varie- 



