August 29, 1913] 



SCIENCE 



305 



nating theme in the whole realm of zoology 

 than " The Infancy of Animals," and we think 

 that the author of the work under this head 

 has succeeded admirably in a difficult task — 

 thaB of presenting a generous measure of sig- 

 nificant fact, with due regard to scientific 

 accuracy, and in readable English. Students 

 of the invertebrates might feel that he was 

 hardly justified in saying that the " child- 

 hood" of animals was a subject which has 

 been strangely neglected. Yet this criticism 

 would apply to most of the higher animals, 

 with which he is mainly concerned. Take 

 from the shelf any standard work upon mam- 

 mals or birds, and you will look in vain for 

 any adequate accounts of the young in most 

 of the species described. If one were to con- 

 sult a large museum instead, with but few 

 notable exceptions, this neglect of the juvenile 

 period of life would be even more apparent. 



The infantile, juvenile, or adolescent phases 

 of animal life, whatever be the names by which 

 we attempt to classify the post-embryonic 

 phases of development, which lead to the adult 

 state, are not only difiicult to correlate with 

 reference to the " accident " of birth, but they 

 are often exceedingly difficult to study. In 

 many cases, our meager information is due 

 to want of opportunity, rather than to lack of 

 effort. Students who have worked for months 

 at the seashore in the vain endeavor to trace a 

 difficult life history, or who have tramped un- 

 numbered miles in search of a particular bird 

 or beast, in order to study its young, certainly 

 need no admonition on this score. 



The early post-embryonic life of animals 

 embraces a very large section of zoology and 

 psychology, and is of equal importance for 

 coinparative anatomy and evolution. The 

 reader will find anatomical and evolutionary 

 problems freely discussed, but the psychology 

 of behavior does not come within the aims of 

 the present work. Of the fourteen chapters of 

 text, all but two of which deal with vertebrates, 

 the most noteworthy are the three devoted to 

 birds (Young Birds in the Nursery, Colora- 

 tion, and Young Birds and the Records of the 

 Past, Chaps. V.-VII.), a field in which the 

 author is well known by his excellent " History 



of Birds," and numerous special contributions. 

 These, as well as the remaining sections, are 

 filled with pertinent and interesting facts, 

 drawn from a wide field, and are imbued with 

 the spirit which, after learning how, is not 

 satisfied until it knows why. 



Of the many perplexing problems which the 

 coloration of animals presents, the retention of 

 stripes in the livery of the young and adult, or 

 in that of the young alone, is of special inter- 

 est to students of evolution. The author main- 

 tains the Darwinian thesis that this character 

 of the young is reminiscent of an ancestral 

 condition. The primitive striped pattern has 

 often been allowed to persist in the early stages 

 of life, because it was either a direct source of 

 protection, or at least because it was not 

 harmful. In other words the mantle of the 

 forefather has been thrust upon the juvenile 

 descendant to protect him, in the absence of its 

 parents, and has often been left there when of 

 no further use. This longitudinal striping, 

 which is found in representatives of all the 

 vertebrates, is not only more characteristic of 

 the young than of the adult, but is more com- 

 mon in species which have retained the great- 

 est number of primitive characters. In the 

 course of growth the stripes tend to break up 

 into spots, which may be retained, or dis- 

 appear, when the animal becomes uniformly 

 colored. The nestlings of the emu and casso- 

 wary, the most primitive of living birds, as the 

 author shows, are more or less completely 

 marked over the entire body with a series of 

 light stripes, on a dark ground, but these 

 marks disintegrate, giving way to an adult 

 plumage of uniform tint. The same condi- 

 tions are repeated in the unrelated grebes, and 

 in other groups of birds where striped nest- 

 lings occur, these markings tend to break up 

 into spots that may be retained or disappear. 

 Similar phenomena occur in mammals. The 

 leopard may be unable to change his spots, or 

 the tiger his stripes, but the lion can, or has, 

 for his cubs still bear the birth mark of an 

 ancestral spotted state. 



Admitting the power of selection, through 

 variation and heredity, to effect such changes 

 for the better protection of young and adult. 



