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Show 1877.] A N T H O B R A N C H I A T E N U D I B R A N C H I A T E M O L L U S C A . 197 as " the worm itself," while the upper lamella, which is really the principal part of the body of the animal, is regarded as a kind of protecting house. The number of species of Doris was increased to 12 by O. F. Miiller in 1776; and subsequently most of them were figured in his ' Zoologica Danica.' Six of the new species, however, do not correspond with Linneeus's genus, and in fact, belong to other sections of the Nudibranchiata. Gmelin followed Miiller, and still further enlarged the genus to include 25 species. The genus Doris, thus made to be almost synonymous with what we now understand as the " Nudibranchiata," was reduced by Cuvier in the ' Tableau elementaire d'Histoire Naturelle,1* 1798, to its original Linncean signification, and shown to include but 7 of the previously enumerated species. In the ' Annales du Museum ' for 1804, Cuvier wrote a classical article on Doris, in which he brought forward 13 species, giving more or less lengthened descriptions of several of them, and figures of six. He divided the genus into ' Les Doris planes,' and ' Les Doris prismatiques.' In 1814, in his memoir on a new classification of Mollusca, De Blainville proposed the name ' Cyclobranches' (Cyclobranchiata) for his 4th order of " Cephalic Mollusca," to include those " which have the organs of respiration symmetrica], hidden or exposed, and placed in a circle on the posterior portion of the body." Cuvier, in 1817, ignored this, and used the same term for the 7th order of the class Gasteropoda, to embrace the Chitons and Patellas. He has been so very generally followed that it would only create confusion now to employ the name in its original meaning. In the same year Cuvier called the whole of the naked-gilled Mollusks " Nudibranches" (Nudibranchiata); and in 1820 Goldfuss, shortly followed by Ferussac, named those with the branchiae surrounding or near the anus on the medio-dorsal line, " Antho-branches" or "Anthobranchiata," the nomenclature now adopted. From the commencement of this century, the number of known species has been largely increased by scientific voyagers and by home workers. In 1817 Risso described 6 Mediterranean species in the 'Journal de Physique,' a number that he increased to 10 in his ' Histoire Naturelle de l'Europe Meridionale' of 1826. In a monograph, " Ueber das Molluskengeschlecht Doris," published in the ' Nova Acta Nat. Cur.' in the latter year, Rapp enumerated 27 forms, among which 6 were new ; several of them he figured. Riippell and Leuckart, two years afterwards, described and figured 12 new species in the ' Atlas zu der Reise im nordlichen Afrika.' Ehrenberg, in 1831, described 15 new varieties in his ' Symbolae Physicae ;' and this naturalist enunciated a somewhat elaborate classification, founded upon differences in the arrangement of the branchial apparatus of the animals before him. His system has not been found to hold good. In the following year, Quoy and Gaimard, in the ' Voyage de 1'Astrolabe,' gave drawings and descriptions of 21 species of Dorididae, all but three of which were new. They were chiefly from the Malayan, Australian, and Pacific Islands. Other naturalists who have principally increased our knowledge of these Mollusks have been : D'Orbigny, to whom we owe 12 or 13 ; Cantraine, who enu- |