BEHAVIOR OF VERTEBRATES 455 



lation for two hours and fifteen minutes, beginning about noon, 

 and the period of gestation was 144 days long. 



He also concludes that the so-called snake piles are due to 

 the sexual impulse and not to the social, for when the sex im- 

 pulse was at its height in the case observed, five males were at 

 the one time endeavoring to copulate with one female. 



Birds. Haggerty (9) presents a clear case of the first perform- 

 ance of a particulai instinctive act of a young bird. A young 

 sparrow hawk, having fallen from its nest with injury to its 

 wing, was removed to the laboratory and reared by hand. It 

 throve and became very gentle. On the third day a small piece 

 of roast beef was placed in the cage ; the hawk seized the meat 

 with one toot, sinking its claws viciously into it. Its feathers 

 became ruffled and its wings outspread. It fluttered about the 

 cage, still holding to the meat. It continued for some time to 

 strike its booty with its bill, the free foot and its wings. Appar- 

 ently the larger the piece of meat and the greater the hunger 

 of the bird, the more pronounced was the reaction. 



Craig (7) shows that the blond ring-dove (Turtus risorius) 

 ' does not instinctively give drinking response to the sight or 

 sound of water nor to the touch of water on distal parts of the 

 body. The young dove first gets its bill in the water by peck- 

 ing at objects in the water. The contact of the fluid on the 

 skin inside the mouth releases the further steps of the act of 

 drinking. Birds will imitate pecking of parents or other birds, 

 but do not imitate the act of drinking as such. 



The same writer (6) has made observations upon the manner 

 in which young birds break out of the egg. The results of these 

 observations confirm those obtained by the early naturalists. 

 The author summarizes these as follows. The bird chips the 

 egg a little at a time with the bill; as it does so it turns around 

 inside the slWl. the axis of rotation coinciding with the long 

 axis of the shell. As a consequence of this form of action, the 

 egg is chipped around the large end in almost a perfect circle. 

 After the circle has been almost or quite completed, the bird 

 pushes in such a way as to force apart the two sections of the 

 shell. 



Phillips (r9) gives the results of some observations on the 

 inheritance of wildness in "English mallards," a game bird 

 long bred on the English preserves. Young ducks of pure 



