. Elements of comparative anatomy. Anatomy, Comparative. 23G COMPARATIVE posterior portion of the body, and in the Ostracoda, as in many Phyllopoda, the two halves of this structure are movably connected with one another on the dorsal surface. In them the valves of the shell extend also over the anterior portion of the body, and so enclose the whole animal. The very peculiar modifications of the integument in the Cirri- pedia are structures of this kind. The fold, which in the Ostracoda is formed into a bivalve shell, is seen in an early stage in the Cirri- pedia. When the animal bec
. Elements of comparative anatomy. Anatomy, Comparative. 23G COMPARATIVE posterior portion of the body, and in the Ostracoda, as in many Phyllopoda, the two halves of this structure are movably connected with one another on the dorsal surface. In them the valves of the shell extend also over the anterior portion of the body, and so enclose the whole animal. The very peculiar modifications of the integument in the Cirri- pedia are structures of this kind. The fold, which in the Ostracoda is formed into a bivalve shell, is seen in an early stage in the Cirri- pedia. When the animal becomes attached by its antennae, the dorsal portion of the integument is converted into a wide sack or mantle (Fig. 119, d ef) which encloses the body; the sack and the enclosed body are united to one another in the cephalic region only. The portion of this sack, which carries the primitive point of attachment, either remains soft and grows out into a stalk - like organ (Lepadidae), or is converted into a broad basal surface (Balanidae). In many Cirri - pedes the whole mantle re- mains soft (Alepas). But most of them acquire firm calcified shell - pieces, which are developed in the outer lamella of the mantle. The rest of the body, with the post-abdomen, which is beset with tendril-like feet, is enveloped in this mantle, which has the form of a shell, and is in connection with the surrounding medium by means of a cleft, which can be closed at will. In the Rhizocephala this mantle-like envelope forms a tube, which is smooth externally, or a disc, which is marked off into symmetrical lobes. A narrow orifice, like that which leads into the mantle cavity of the Cirripcdia, leads into a space which corresponds to this mantle cavity, and functions as a marsupial pouch. In the Cirripedia part of the typical crustacean body, with its appendages, is enveloped by the mantle, and permanently retains its structure; but in the Rhizo- cephala the whole surface of the jointed body becomes conve
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectanatomycomparative
