File:Biology and man (1944) (19760645044).jpg

Title: Biology and man
Identifier: biologyman00grue (find matches)
Year: 1944 (1940s)
Authors: Gruenberg, Benjamin C. (Benjamin Charles), 1875-1965; Bingham, N. Eldred (Nelson Eldred), 1901-
Subjects: Biology; Human beings
Publisher: Boston, New York, (etc. ) Ginn and company
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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New York Zoological Society A VIVIPAROUS SNAKE In the garter snake and in some other species, the fertilized eggs remain within the body of the mother until the young are developed to the adult form Most reptiles and some birds leave the eggs, which are hatched by the heat of the sun or at ordinary temperatures. Most of the common birds, however, build more or less elaborate nests and keep the eggs warm during hatching. And most birds care for the fledglings, as well as the eggs. In many species the young learn their "song" from the parents or other older birds. Domesticated canaries are sometimes trained as songbirds, or at least protected against un- desirable noises, since they are very imitative. The feeding of young birds by the parents is a very interesting operation to watch, as it shows the de- velopment of rather complex instincts. Infancy among Mammals We consider the mammals the highest class of vertebrates—and indeed of all living things. In this class the dependence of the young upon their parents is carried to the greatest extreme. In the entire class the female develops special milk glands—hence the name, from mammae, the breasts or teats. Related to the presence of the milk gland is the infant's equipment of nerve-and-muscle sucking mechanism, and his complete dependence upon the milk supply for his nourishment. In the marsupials the egg hatches within the uterus of the mother, as in the "true mammals", but the fetus leaves at a rather early stage — in the 422

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