The evolution of man : a popular exposition of the principal points of human ontogeny and phylogeny . These cells pass directly fromthe germ-glands into the ccelom, and are discharged througha posterior aperture in the abdomen. The condition of theprimitive kidneys in these is, however, very interesting, and throws light on the complex kidneystructure of the higher the first place, in the Myxi-noicles (Bdellostoma) we find a longtube, the primitive kidney duct(protureter, Fig. 317, a), on eachside. This opens internally intothe ccelom through a ciliated funnel-shaped aperture (a
The evolution of man : a popular exposition of the principal points of human ontogeny and phylogeny . These cells pass directly fromthe germ-glands into the ccelom, and are discharged througha posterior aperture in the abdomen. The condition of theprimitive kidneys in these is, however, very interesting, and throws light on the complex kidneystructure of the higher the first place, in the Myxi-noicles (Bdellostoma) we find a longtube, the primitive kidney duct(protureter, Fig. 317, a), on eachside. This opens internally intothe ccelom through a ciliated funnel-shaped aperture (as in RingedWorms); it opens externally throughan opening in the outer skin. Agreat number of small horizontaltubes ( segmental canals, or primi- Fig. 317.—A. Portion of kidney of Bdel-lostoma : a, primitive kidney duct (prohi-reter); o, segmental canals, or primitiveurine canals {iiibuli uriniferi); c, kidney-vesicles (capsulce Malphigiance).—B. Por-tion of the same, much enlarged : c, kidney-vesicle, with the glomerulus ; d, approachingartery ; e, retreating artery. (After JohannesMullcr.). tive urine tubes) open on its inner side. Each of theseterminates in a blind, vesicular capsule (c) enclosing a THE PRIMITIVE KIDNEY OF SKULLED ANIMALS. 407 knot of blood-vessels (glomerulus, an arterial net, , B, c). Afferent arterial branches (vasa afferentia) con-vey arterial blood into the coiled branches of the glome-rulus (d), and efferent arterial branches (vasa efferentia)again carry it out of the glomerulus (e). In Primitive Fishes (Selachii) also there is a longitudi-nal series of segmental canals, which open outwardly inthe primitive kidney ducts. The segmental canals (a pairin each metameron of the central part of the body) open, inthis case, freely into the body-cavity, through a ciliatedfunnel (as in Ringed Worms, or Annelids). A part of thisorgan forms a compact primitive kidney, while the rest isemployed in the formation of the sexual organs. The primitive kidney
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Keywords: ., book, bookcentury1800, bookdecade1870, booksubjectembryologyhuman
