76 The Recapitulation Theory and Human Infancy 



but represent what we may call scaffolding features which 

 have been introduced solely for the benefit of the individual. 

 The study of young mammals does, nevertheless, throw a 

 flood of light bearing on their ancestry. . . ,' 722 



It must be noted that both writers, by the terms infancy 

 and youth, refer not only to that period of plasticity in the early 

 life of animals of the learning type, but to the period following 

 hatching whether plastic, larval, or merely precocious and essen- 

 tially unmodifiable, as with growing reptiles. If we limit the 

 application of their remarks to the period of plastic neuro-mus- 

 cular development, certain other statements of these authors 

 should be considered. Mitchell, for instance, with reference 

 to the mammals, the group in which the period of plastic infancy 

 is most conspicuous, writes as follows: 



" Mammals, when they are born or very soon afterwards, 

 closely resemble their parents. The differences are due to 

 greater likeness to ancestors and to their nearest allies, to the 

 absence of special weapons or ornaments, or to the presence of 

 characters useful to the young themselves." 23 



One gathers that the period of youth among mammals is not 

 essentially recapitulatory but rather adaptive and anticipatory. 

 Nevertheless, both these authors present a very considerable 

 number of youthful characteristics which they explain as re- 

 tained ancestral features. From the account of Py craft are to 

 be noted the following: certain cases of " milk-teeth "; horns of 

 ruminants; antlers of deer; the presence of a hairy covering 

 which does not persist; the under-fur of one group of seals; 

 spines in certain Insectivora; and the familiar ape-like features 

 of the human infant. Pycraft concludes his list with the remark, 

 "We might add considerably to the number of instances of this 

 kind." 



In the matter of coloration the case is complicated and some 

 difference of opinion is expressed, yet the two authors agree in 

 the statement that the young of mammals very commonly 

 show differences in coloration when compared with adults, the 

 youthful coloration being regarded by both as older, the adult 

 as a later modification. 



Mitchell, The Childhood of Animals, p. 40. 

 Op. cit., p. 13. 



