176 SEXUAL SELECTION: BIRDS. [Part II. 



possible. Young lions and pumas are marked with feeble 

 stripes or rows of spots, and, as many allied species both 

 young and old are similarly marked, no naturalist, who 

 believes in the gradual evolution of species, will doubt 

 that the progenitor of the lion and puma was a striped 

 animal, the young having retained vestiges of the stripes, 

 like the kittens of black cats, which when grown up are 

 not in the least striped. Many species of deer, which 

 when mature are not Spotted, are while young covered 

 with white spots, as are likewise some few species in their 

 adult state. So, again, the young in the whole family 

 of pigs (Suidae), and in certain rather distantly-allied ani- 

 mals, such as the tapir, are marked with dark longitudinal 

 stripes ; but here we have a character apparently derived 

 from an extinct progenitor, and now preserved by the 

 young alone. In all such cases the old have had their 

 colors changed in the course of time, while the young 

 have remained but little altered, and this has been effect- 

 ed through the principle of inheritance at corresponding 

 ages. 



This same principle applies to many birds belonging 

 to various groups, in which the young closely resemble 

 each other, and differ much from their respective adult 

 parents. The young of almost all the Gallinaceas, and of 

 some distantly-allied birds such as ostriches, are, while 

 covered with down, longitudinally striped ; but this charac- 

 ter points back to a state of things so remote that it hard- 

 ly concerns us. Young cross-bills (Loxia) have at first 

 straight beaks like those of other finches, and in their im- 

 mature striated plumage they resemble the mature redpole 

 and female siskin, as well as the young of the goldfinch, 

 greenfinch, and some other allied species. The young of 

 many kinds of buntings (Emberiza) resemble each other, 

 and likewise the adult state of the common bunting, E. 

 miliaria. In almost the whole large group of thrushes 



