CHAPTER XXIX 

 THE HUMAN BABY 



IT is to the young of animals that we look, as a rule, to 

 find evidences of the lingering of ancestral habits. Evi- 

 dences of an ancestral arboreal habit might possibly 

 linger under some guise or other in the young of an animal 

 which, descended from an arboreal stock, has ceased to 

 make its home among the branches. 



A striking illustration of the converse of this expecta- 

 tion may perhaps make the argument more clear. Among 

 the birds, the whole family of the Terns (Sternidce] is 

 characterized by a typically terrestrial habit of incubation, 

 for their eggs are laid upon the bare ground. It is true 

 that some species make a slight attempt at nest-building, 

 and some meagre wisps are brought together to line a 

 shallow depression in the beach shingle. In the case of 

 one member of the family (Anous stolidus), this nest may 

 rise, as a collection of sea-wrack, to the dignity of being 

 a little mound; but the general rule is that the egg is 

 laid bare upon the ground. The Tropic Island White 

 Tern (Oygis Candida] has, however, taken to an arboreal 

 life, and it lays its solitary egg upon the branch of a tree. 

 No nest whatever is constructed, and no attempt is made 

 to insure the safety of the egg beyond selecting a spot 

 upon a branch where some irregularity of the bark will 

 prevent it freely rolling away. Although in this business 

 of finding a suitable place, in balancing a naked egg 

 upon a bare branch, and in the whole process of sitting 

 upon this delicately poised egg, the adults show a very 

 complete adaptation to their new surroundings, the 

 offspring is hatched as an obviously terrestrial creature. 

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