. A textbook of invertebrate morphology [microform]. Invertebrates; Morphology (Animals); Invertébrés; Morphologie (Animaux). TYPE MOLLUSC A. 315 modifications of portions of the foot, being innervated from the pedal ganglia. In these forms also fringed or simple pro- cesses of the posterior portion of the body occur which serve as respiratory organs, though they are not homologous with tJie true branchia which in Pneumoderma coexist with them. 3. Suborder Nudihmnchia. In the Nudibranchs the visceral hump has undergone elongation parallel with the long axis of the foot, from which it is not di
. A textbook of invertebrate morphology [microform]. Invertebrates; Morphology (Animals); Invertébrés; Morphologie (Animaux). TYPE MOLLUSC A. 315 modifications of portions of the foot, being innervated from the pedal ganglia. In these forms also fringed or simple pro- cesses of the posterior portion of the body occur which serve as respiratory organs, though they are not homologous with tJie true branchia which in Pneumoderma coexist with them. 3. Suborder Nudihmnchia. In the Nudibranchs the visceral hump has undergone elongation parallel with the long axis of the foot, from which it is not distinctly marked off, and an apparent bilateral sym- metry is manifested by the body. This condition, however, is evidently entirely secondary, as is shown by the structure of the heart and nephridium, in which the usual asymmetry is well marked. There is no shell, mantle, or ctenidia. Adaptive branchiie are, however, frequently developed, as in Pleurophyl- lidia, where they form a series of folds which lie in a groove at the side of the body and recall somewhat the arrange- ment in the Chitonidie, or in Doris, where they surround the anus, which has a dorsal position, and form a circle of pin- nate processes. In the pelagic PhyUirhoe and in the creeping Limaponfia, however, there is no trace of respiratory organs. Many forms (Fig. 141), such as Mali's, FacelUna, and their allies, bear upon the dorsal surface of the body numbers of fiuger-Iike processes usually arranged in bunches, and frequently brightly colored. These cemfa frequently enclose branches from the intestine which correspond to the digestive gland of other forms, and „ ,,, ' bear at their extremities a sac in which " ' ~ ^'^"'""^^• are developed uematocysts. Tliese organs are usually richly provided with blood- vessels, and are probably respiratory in function. thonL'h the presence of uematocysts renders it probable tliat they are also protective—an idea which is confirmed by their. CHIA
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