File:Image from page 139 of "Introduction to zoology; a guide to the study of animals, for the use of secondary schools;" (1900) (14598295450).jpg

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

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Text Appearing Before Image: ^ begin to grow outat the place of injury, and at least one moult is necessaryfor their complete restoration. Abnormalities in the claws of the lobster are not un-common. The thumb-like protuberances of the next to the last of the joints of the great claw is sometimes bifid,or carries a large wart. The finger which opposes thethumb is also sometimes forked (Fig. 116). Many ofthese abnormalities are probably due to injury of the claw;but others cannot be explained in this way. For instance,cases have been observed of lobsters having crushingclaws of equal size on the two sides of the body. Anantenna has been seen replacing an eye, and this resultmay be obtained by cutting off an eyestalk near its base 120 ZOOLOGY

Text Appearing After Image: when an antenna will regenerate (Fig. 117), one or twoextra oviducts may occur, or double monsters — sort of Siamese twins - - may be hatchedout. Similar monstrosities arefound in other arthropods. Physiological Division of Labor.The difference between a highly developed animal and alowly organized one is not firstof all a difference of size nor adifference in the number of parts,- just as a large population ornumerous cities are not the pri-mary characteristics of a highlycivilized state. But just as acomplex civilization is one inwhich each of the different citizenshas his own special task to per-form for the commonwealth, soa highly developed organism isone in which each different oreran o has its special role to play. Theworm Nereis has more segments o to the body than the crayfish, butthese segments are very nearlyalike — the parapodia especially FIG. lib.—Two abnormal claws. J Upper figure shows a double are quite similar. In the crayfish, CrCe°ther^TextS ° the other han

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