Identifier: evolutionanimall00jord (
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Evolution and animal life; an elementary discussion of facts, processes, laws and theories relating to the life and evolution of animalsYear:
1907 (
1900s)Authors:
Jordan, David Starr, 1851-1931 Kellogg, Vernon L. (Vernon Lyman), 1867-1937Subjects:
EvolutionPublisher:
New York, D. Appleton and CompanyContributing Library:
MBLWHOI LibraryDigitizing Sponsor:
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view book online to see this illustration in context in a browseable online version of this book.Text Appearing Before Image:coarsely organized birds,such as the chicken, the duck, and the auk, as with the reptiles,the young animal is hatched with well-developed muscularsystem and sense organs, and is capable of running about, and,to some extent, of feeding itself. Birds of this type are knownas prsecocial, while the name altricial is applied to the morehighly organized forms, such as the thrushes, doves, and songbirds generally. With these the young are hatched in a whollyhelpless condition, with ineffective muscles, deficient senses,and dependent wholly upon the parent. The altricial conditiondemands the building of a nest, the establishment of a home,and the continued care of one or both of the parents. The very lowest mammals known, the duck bills (Mono-tremes) of Australia, lay large eggs in a strong shell like thoseof a turtle, and these they guard with great jealousy. But ADAPTATIONS 339 with almost all mammals the egg is very small and withoutmuch food yolk. The egg begins its development within theText Appearing After Image:FIG. 199.—Kangaroo, Macropus ruftts, with young in pouch. body. It is nourished by the blood of the mother, and afterbirth the young is cherished by her, and fed by milk secretedby specialized glands of the skin. All these features are 340 EVOLUTION AND ANIMAL LIFENote About Images Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.