Evolution and animal life; an elementary discussion of facts, processes, laws and theories relating to the life and evolution of animals

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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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cter, the influence, the regularity or irregu-larity of variations, their behavior in heredity, whether trans-missible or not, whether acquired or congenital, whether deter-minate or indeterminate, etc.—these are the problems that thefactor variation or variability presents to biologists. Heredity,too, has its problems. These we shall take up in anotherchapter. That variations exist is too obvious to everyone to need anydiscussion. Any litter of kittens or puppies, of mice or pigs,shows us the differences in pattern, shape, and physiology of in-dividuals born at one time and of the same parents. In wildnature the variations among brothers and sisters are no less realthan among these domesticated animals. 131 132 EVOLUTION AND ANIMAL LIFE Collect a few thousand individuals, at one time in one place,of a single species of insect, as a spotted ladybird beetle; thengo over these carefully, looking for variation in some singlecharacteristic, as the color pattern. What do you find? Let us
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FIG. 72.—Diagram showing variation in elytral pattern of the convergent ladybird,Hippodamia convergens : 1, Mode; 2-9, variations in size of spots; 10-17, variationsby coalescence of spots; 18-40, variations by reduction in number of spots. (AfterKellogg and Bell.) VARIATION AND MUTATION 133 answer by calling attention to Figs. 72, 73, and 74 and whatthese variations signify. Note also Fig. 75, showing the

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