CLASSIFICATION AND ADAPTATION 21 



attributes can make a perceptible difference to the 

 prospect of success, than that an indefinite and im- 

 palpable change should entail such consequences.' 

 Here the distinction between adaptive and non- 

 adaptive characters is recognised, but both are 

 emphatically attributed to the same origin. 



The American evolutionist, T. H. Morgan, also a 

 specialist in Mendelism, goes further, and maintains, 

 not merely that mutations which happened to make 

 a ' difference to the prospect of success ' survived, 

 or were selected, but that if a mutation arising from 

 a change in the gametes was not compatible with 

 the conditions of the animal's life at the time, it 

 either died, or found other conditions, or adopted 

 new habits which were adapted to the new char- 

 acter or structure. He takes Flat-fishes as an 

 example, and suggests that having by mutation 

 become asymmetrical, and having both eyes on one 

 side, etc., the fish adopted the habit of lying on the 

 ground on one side of its body. This is, of course, the 

 exact opposite of the older conception : the struc- 

 ture of the animal has not been changed by new 

 habits or conditions, but new habits and conditions 

 have been sought and found in order to meet the 

 requirements of the change of structure. 



The present wi^iter, on the other hand, believes 

 that not only are adaptive characters distinct from 

 non-adaptive specific characters, and from non- 

 adaptive diagnostic characters in general, but that 

 their origin and evolution are entirely distinct and 

 different. There are two separate problems, the 

 origin of adaptations and the origin of species, and 

 the investigation of these two problems leads not to 

 one explanation common to both, but to two enthely 



