. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative. 354 COMPARATIVE ANATOMY in which they are shorter and more compact, and are confined to the middle portion of the coelome. In Urodeles they always consist of a narrow anterior, and a broader and more compact posterior portion. The latter, as in Elasmobranchs, gives rise to the functional kidney (Fig. 279), while the former becomes connected in the male with the generative organs. Delicate vasa efferentia, developed from the mesonephros, pass out from the testis (Figs. 279, 280, 292) into the substance of the kidney, an
. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative. 354 COMPARATIVE ANATOMY in which they are shorter and more compact, and are confined to the middle portion of the coelome. In Urodeles they always consist of a narrow anterior, and a broader and more compact posterior portion. The latter, as in Elasmobranchs, gives rise to the functional kidney (Fig. 279), while the former becomes connected in the male with the generative organs. Delicate vasa efferentia, developed from the mesonephros, pass out from the testis (Figs. 279, 280, 292) into the substance of the kidney, and there open into the renal tubules; they may either enter the kidney direct, or else open first into a longitudinal collecting duct, from which fine canals pass to the tubules. Thus the seminal fluid passes through the nephridia as well as through the Wolffian duct, which serves as a urinogenital duct. In Urodela and Anura of both sexes the Wolffian duct nearly always opens separately on either side into the cloaca, receiving first, in Urodeles, a number of ducts from the posterior part of the kidney (compare Elasmobranchs, p. 350). In Anura the Wolffian ducts pass some distance indepen- dently along the body-cavity, in correspondence with the position of the kidneys, and a seminal vesicle opens into each (Fig. 281). The urinary (allantoic) hladder (see p. 259) opens into the cloaca ventrally, opposite to the urino- genital apertures. In its simplest TT TT ⢠â . , .,r ,^ ^"^"^ ^* ^^ finger-shaped (, Siren, ''^^ir4XtZSi Proteus), but it usually becomes surface of the kidneys at t; ,?, Swollen distally and is often bi- " lobed: in Alytes and Bombinator it forms a double sac. Slight indications of a seg- mental arrangement are found only ,, , ., n TT , , . in the anterior sexual portion of the kidney of Urodeles; in the posterior part, and in the entire kidney of Anura, all traces of segmentation have disappeared In both cases, however, the nephrostomes
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectanatomycomparative
