Identifier: evolutionanimall00jord (find matches)
Title: Evolution and animal life; an elementary discussion of facts, processes, laws and theories relating to the life and evolution of animals
Year: 1907 (1900s)
Authors: Jordan, David Starr, 1851-1931 Kellogg, Vernon L. (Vernon Lyman), 1867-1937
Subjects: Evolution
Publisher: New York, D. Appleton and Company
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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FIG. 274.—Nest and eggs of the Rufus hummingbird, Trochihts rufus. (Photograph byJ. O. Snyder, Stanford University, California.) maintenance of the species is much less, and the opportunitiesfor specialization in other relations of life are much greater.In these regards, the nest-building and home-making animalshave the advantage over those that have not these instincts. 442 EVOLUTION AND ANIMAL LIFE The animals that mate for life have the advantage over polyg-amous animals, and those whose social or mating habits give
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FIG. 27o.—Altricial nestlings of the blue jay, Cyanocitta c/istata. rise to a division of labor over those with instincts less highlyspecialized. When we study instincts of animals with care and in detail,we find that their regularity is much less than has been sup-posed. There is as much variation in regard to instinct among REFLEXES, INSTINCT, AND REASON 443 individuals as there is with regard to other characters of thespecies. Some power of choice is found in almost every opera-tion of instinct. Even the most machinelike instinct showssome degree of adaptability to new conditions. On the otherhand, in no animal does reason show entire freedom fromautomatism or reflex action. The fundamental identity ofinstinct with intelligence, says an able investigator, is shownin their dependence upon the same structural mechanism (thebrain and nerves), and in their responsive adaptability.

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