. Elements of comparative anatomy. Anatomy, Comparative. 610 COMPAEATIVE ANATOMY. in the Cyclostomata. The ovaries of the Petromyzontes have the form of paired lamellas, which extend along the ccelom, and are thrown into a large number of folds, in which the ova are developed. The testes are similar in character. In the Myxinoidea the germ- glands are unpaired, and arise from the right side of the mesentery. Both sets of generative products are passed into the cosloin, whence they reach the exterior through the abdominal pore. The ovaries of some Teleostei have almost the same characters ; thu
. Elements of comparative anatomy. Anatomy, Comparative. 610 COMPAEATIVE ANATOMY. in the Cyclostomata. The ovaries of the Petromyzontes have the form of paired lamellas, which extend along the ccelom, and are thrown into a large number of folds, in which the ova are developed. The testes are similar in character. In the Myxinoidea the germ- glands are unpaired, and arise from the right side of the mesentery. Both sets of generative products are passed into the cosloin, whence they reach the exterior through the abdominal pore. The ovaries of some Teleostei have almost the same characters ; thus, in the Salmonidas the eggs are passed into the abdominal cavity, and are evacuated through the abdominal pore. The same is the case in Lcemargus borealis among the Selachii, where the ovaries contain much smaller eggs, and are themselves much larger. In the rest of the Fishes there are efferent ducts in both sexes, which are largely—perhaps always—due to the differentiations which affect the primitive kidneys (cf. § 448). In this relation the Ganoi'dei are of a low grade, for their germ-glands have no direct ducts, and their products are passed into the ccelom. In both sexes the products escape by an apparatus which is homologous with the Mullerian duct, consisting of a canal of varying length, and provided with an infundibular orifice, which is attached to the ureter (secondary archinephric duct); this takes up the generative products. This fact must be regarded as one of special importance, for we learn from it that the Mullerian duct may be turned to use in the male. The presence of this duct in both sexes leads to a correct apprehension of the real facts of the case, and renders it unnecessary to regard the presence of the rudiments of these organs in the male as due to a primitive hermaphroditism, which, cannot be shown to have obtained at the required stage of development. Two different arrangements can be derived from that which is dominant in the Ganoidei. One i
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectanatomycomparative
