Image from page 199 of "Introduction to zoology; a guide to the study of animals, for the use of secondary schools;" (1900) (14784669612)

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

Text Appearing Before Image:

ality. Even the small, imperfectpearls are of value, since they are ground up to make thepowder used in polishing the more valuable pearls. The spawning season of our Unioimhe is short. Theeggs pass, during the latter part of October, into the gillsof the parent, where they undergo their early development,protected by the parent shell and supplied richly withoxygen. The cleavage is unequal because of the larger 180 ZOOLOGY amount of yolk in some of the cells than in the others.Eventually a shell is formed, which divides into two valvesunited by a straight hinge. A spine is formed on the freeedge of each valve, and a thread (byssus thread) is secretedfrom the body. The young at this stage is known asGlochidium (Fig. 165). In the spring Glochidia becomefree from the mother, and attach themselves to the gills orfins of a fish by means of the spines on the shells. Herethey become transformed. The single adductor muscle dis-appears, and becomes replaced by the two characteristic of R B. J.

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anodonta introduction to zoology a guide to the study of animals for the use of secondary schools unionidae anatomy book illustrations anatomical atlas anatomy zoology animals images from internet archive

1944

Image from page 199 of "Introduction to zoology; a guide to the study of animals, for the use of secondary schools;" (1900)

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