Image from page 339 of "Introduction to zoology; a guide to the study of animals, for the use of secondary schools;" (1900) (14784788122)

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Geomys tuza =G. pinetis, others Identifier: introductiontozo00dave Title: Introduction to zoology; a guide to the study of animals, for the use of secondary schools; Year: 1900 (1900s) Authors: Davenport, Charles Benedict, 1866-1944 Davenport, Gertrude Anna Crotty, 1866- Subjects: Zoology Publisher: New York, Macmillan company London, Macmillian and co., ltd. Contributing Library: MBLWHOI Library Digitizing Sponsor: MBLWHOI Library View Book Page: Book Viewer About This Book: Catalog Entry View All Images: All Images From Book Click here to view book online to see this illustration in context in a browseable online version of this book. Text Appearing Before Image: continu-ously throughout life, and are not formed, once for all, likeour teeth. In addition to plant materials, rats and miceeat a certain amount of animal food. The different races of tame mice illustrate the resultsobtained by preserving sports and selecting the best forbreeding purposes. The white mouse, for instance, is an 320 ZOOLOUY albino ; that is, an animal without pigment. Albinos oc-cur among almost all kinds of mammals, but the cause ofthem is unknown. So, likewise, the black race of tamemice is due to an excess of pigment, a sport found nowand then among other mammals. The pure reddish brownraces have probably been produced by selecting the housemice with little black in the fur. By preserving occasionalsports and by selecting for breeding the purest-coloredindividuals, all the different races of our domestic animalsand plants have been established and improved. Other Rodents. — The mouse belongs to the group Ro-dentia,1 distinguished from other mammals by the fact that Text Appearing After Image: Fi