. Elements of biology, with special reference to their rôle in the lives of animals. Biology; Zoology. MULTICELLULAR ANIMALS 139 PROSTOMIUM SEGMENT 10 SEGMENT 14 SEGMENT 15 CLITELLUM 'iEGMENTS 31-37. MOUTH SPERMATHECAL OPENINGS OVIDUCT OPENING SPERM DUCT OPENING â SEGMENT larger space required by reproductive and excretory organs, fill the ccelom and its divisions (Fig. 65). The distinctive feature of the Annelida is the division of the body into segments or meta- meres. Metamerism is most highly developed in this phy- lum; it continues to be a char- acteristic of the structure of more advanc
. Elements of biology, with special reference to their rôle in the lives of animals. Biology; Zoology. MULTICELLULAR ANIMALS 139 PROSTOMIUM SEGMENT 10 SEGMENT 14 SEGMENT 15 CLITELLUM 'iEGMENTS 31-37. MOUTH SPERMATHECAL OPENINGS OVIDUCT OPENING SPERM DUCT OPENING â SEGMENT larger space required by reproductive and excretory organs, fill the ccelom and its divisions (Fig. 65). The distinctive feature of the Annelida is the division of the body into segments or meta- meres. Metamerism is most highly developed in this phy- lum; it continues to be a char- acteristic of the structure of more advanced animals up to and including Man. The earth- worm, while not a typical an- nelid, is one with which most are somewhat familiar and serves to illustrate metamerism for our purposes here. An ex- amination of the anatomy of an earthworm shows it to consist of a series of rings (Fig. 83). In the posterior region these rings are practically alike, each containing the same organs similarly arranged and each separated from adjacent meta- meres by the septae which ex- tend across the coelom. The body therefore consists of a series of secondary individu- als, or partial individuals, each closely resembling adja- cent members. In an ideal segmental animal all metameres would be identical and each would be provided with appendages for loco- ANUS Fig. 83.âExternal appearance of the com- mon Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Buchanan, James William, 1888-. New York, London, Harper & brothers
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