. The Cambridge natural history. Zoology. 398 FISHES CHAP. tomes lose their connexion with the myocoeles, although they still retain their " nephrostomes " or apertures through which they communicate with the ventral coelom. When fully developed the pronephros consists of a few tubules, more or less convoluted, open- ing at their inner extremities into the coelom by means of their ciliated nephrostomes, and at their outer ends communicating with the exterior through the archinephric duct. In relation. mnf Fig. 229.—Diagrammatic transverse sections througli an embryo Craniate to show
. The Cambridge natural history. Zoology. 398 FISHES CHAP. tomes lose their connexion with the myocoeles, although they still retain their " nephrostomes " or apertures through which they communicate with the ventral coelom. When fully developed the pronephros consists of a few tubules, more or less convoluted, open- ing at their inner extremities into the coelom by means of their ciliated nephrostomes, and at their outer ends communicating with the exterior through the archinephric duct. In relation. mnf Fig. 229.—Diagrammatic transverse sections througli an embryo Craniate to show the mode of development of the pronephros (A) and of the mesonephros (B). The right side of each figure shows an earlier stage than the left. In B (left side) the con- nexion of a vas efferens with a mesonephric tubule, and the division of the archi- nephric duct into Miillerian and mesonephric ducts are shown, a. Aorta ; ax, alimentary canal ; , archinephric duct ; g, glomus ; gl, glomerulus ; , iainer nephrostome ; mb, Malpighian body ; vid, Miillerian duct ; mnd, mesonephric duct; mnt, mesonephric tubule ; mt/c, myocoele ; myt, myotome ; n, notochord ; np, nephrotome ; nt, nephrostome ; , outer nephrostome ; , pronephric tubule ; , spinal cord ; t, testes ; , ventral coelom ; , vas efferens. (After Kingsley and Semon.) with the pronephros a branch from the dorsal aorta forms a tuft of capillary blood-vessels or " glomus," opposite the nephrostomes, which projects into the ventral coelom on each side. Later, a second series of much more numerous tubules is formed behind the pronephros, which constitute the mesonephros. In forming mesonephric tubules the nephrotomes become disconnected from the myotomes and their myocoeles, and curving outwards they epiblast; hence the suggestion that in the primitive Vertebrates the duct was a longitudinal groove in the superficial skin into which the pronephric tubules opened Please note that t
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
