Identifier: animansmanelemen00kell (find matches)
Title: The animans and man; an elementary textbook of zoology and human physiology
Year: 1911 (1910s)
Authors: Kellogg, Vernon L. (Vernon Lyman), 1867-1937 McCracken, Mary Isabel
Subjects: Zoology Physiology
Publisher: New York, H. Holt and company
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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or, better, of an injecting mass of gelatine(see Appendix I) is injected into the heart through the needle of a hypo-dermic syringe. For the purpose of injecting, a small bit of the shell maybe removed from the cephalothorax above the heart. Specimens whichare to be kept for some time should be placed in alcohol or 4% formalin. External structure (fig. 10).—Place a specimen in a panfor study. Note that the body, which of course differs muchin shape from that of the toad, is also unlike that of thetoad in being covered by a hard calcareous exo-skeleton,which acts as a covering for the soft parts and also as a placeof attachment for the muscles, just as the internal skeletondoes in the case of the toad. The body is composed of ananterior part, the cephalothorax, and a posterior part, theabdomen. The cephalothorax is covered above and on thesides by the carapace, which is divided into parts correspond-ing to the head and thorax of the toad by the transverse 28 THE CRAYFISH 29 antennule
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opening of green gland \ maxillipeds—f- thorax genital aperture antennachela waljcing legs FIG. 10. Ventral aspect of crayfish, Cambarus sp. with the appendagesof one side disarticulated. 30 THE ANIMALS AND MAN cervical suture. The abdomen is composed of segments.How many? The flattened terminal segment is called thetelson. Is the cephalothorax composed of segments ? Whereis the mouth of the crayfish? Where is the anal opening? At the anterior end of the cephalothorax note a sharpprojection, the rostrum. Where are the eyes ? Remove oneof them and examine its outer surface with a microscope. Abit of the outer wall should be torn off and mounted on aglass slide. Note that it is made up of a great many littlefacets placed side by side. Each of these facets is the exter-nal window of an eye element or ommatidium. An eye com-posed in this way is called a compound eye. In front of theeye note two pairs of slender many-segmented appendages.The shorter pair, the antennules, are two-branched

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