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 88 THE CONDOR Vol. XIX ure out the biological reasons for the various developments ]n nidification are comprised in a few pages of printed matter. A.R. Wallace has given an interest- ing theory of the relation of the nest to the coloration of the species building it, in his "Theory of Birds' Nests" (Journal of Travel and Natural History, 1868). This has been discussed and criticised by Dr. J. A. Allen, in the Bulletin of The Nuttall Ornithological Club. A few limited and cursory discussions of various phases of the subject are given in various general works such as Knowlton's "Birds of the World", but no extended study of the subject has been made. Just why the individuals of one generation of a, given species in the animal kingdom should occupy themselves in any manner with the rearing of the suc- ceeding generations is a philosophical enigma, for after the production and fer- tilization of the egg no physical necessity of their own is satisfied by it. Never- theless we find the beginnings of such care even among the lowest animals. N]d]fication first appears n the vertebrates among the aquatic forms, for among fishes the little stickleback and the pugnacious sunfish guard their nests with great fearlessness, while the humble bullhead, after the eggs are hatched, may be seen leading his dusky young about as they learn the business of fish life. Fish nests are usually very simple affairs, being seldom more than shallow basins in the stream bottom, but when we get among the higher vertebrates we find more ambitious structures. For among all vertebrates the nest has reached its nost elaborate development with man, though in the other great group of warm- blooded vertebrates, the birds, it has reached a development in which many nests show a wonderful ingenuity and exquisite care in construction. The nesting habit among birds is probably anticipated by the nesting habits which are found among reptiles, as from the ancient reptilian group of Dinosaurs have probably arisen our modern birds. The nesting habits of the higher modern reptiles and some of the more primitive birds are so similar that they can be said to bridge over the gap from the slovenly nidification of the average indifferent reptile to that solicitous care of the young characteristic of the highest birds. Many of the modern snakes deposit their eggs in holes in the ground or in the soft wood of rotten stumps, and turtles dig jug-like holes in the sand. Some tropical alligators deposit their eggs in warm sandbanks,. while those found in the cooler latitude of the southern states bring together a mass of rotting vegetation, by the warmth of which the eggs are hatched, after which the young are guarded for a tine by the mother. Now this method of nesting occurs among some of the lower birds, though here it is a reversion from, or more probably a special devel- opment of, the general bird type. The interesting fowls which have this primi- tive nesting habit are the Megapodes of the Australian region. Of these, the Aus- tralian Brush Turkey (Catheturus lathami) rakes together a pile of decaying leaves and rotten wood, and n this mound at intervals deposits its eggs, which are incubated by the heat from the decomposition of the nest materials. Other members of this same curious group deposit their eggs in the warm sands of the sea shore, where they sre left without further care. Similar to this were probably the beginnings of the nesting habit among birds. Careful guarding of the eggs early developed into a definite period of in- cubation, which was made possible by the high temperature of the body. The de- velopment of the four-chambered heart meant the possibility of the great devel- opment of the brain, as this delicate organ was no longer poisoned by qiantities of venous blood; tlen, with this increase in brain power, could come the dexterity and ingenuity displayed by the average bird in constructing his home.