254 A STUDY IN HEREDITY 



has thereby been straightened, shortened, and simplified, and the 

 evolution of new characters, useful in the new environment, has 

 become possible. Thus, for instance, has been rendered possible 

 the higher characters of man, for even after birth he is closely 

 protected, and, therefore, even in that portion of the ontogeny 

 which intervenes between the infant and the adult has there been 

 much retrogression. Consider how feeble and helpless is the 

 infant after birth ; but its prototypes of the phylogeny fought for 

 their own existences. The infant can digest scarcely anything but 

 milk, and its jaws are very feeble. Its prototype must have had 

 much wider powers of digestion. Perhaps more remarkable than 

 anything else is the retrogression of instinct in man. I have dealt 

 at length with this question elsewhere, and have not space for it 

 here ; but consider how helpless is the infant at birth, how 

 extremely incapable, as compared to young insects, for instance, 

 of adapting itself, of its own initiative, to the environment. Later 

 on it acquires all kinds of knowledge and ways of thinking and 

 acting, which serve as superior substitutes for instinct. But 

 meanwhile the mother's protection, which has rendered possible 

 this acquirement, has rendered useless also the instincts of its 

 prototypes, which have therefore been lapsed. Hence the retro- 

 gression of instinct in man. By it his mental ontogeny is 

 shortened and simplified, just as by the retrogression of bodily 

 parts his physical ontogeny is shortened. 



In the foregoing I have spoken of characters lapsing in orderly 

 succession, the last first, the earlier later. But it seems to me 

 probable that earlier characters may sometimes lapse before the 

 later. This may happen when some parts of the phylogeny, and 

 consequently of the ontogeny, are not direct, but form a loop, so 

 to speak. The omission of the loop would straighten, and there- 

 fore shorten, the ontogeny, and considering how condensed is the 

 latter, I believe that this must often occur. 



