Elements of comparative anatomy (1878) Elements of comparative anatomy elementsofcompar00gege Year: 1878 EXCRETORY ORGANS OF VERTEBRATA. 605 which, however, several ureters may open separately. In the females, also, the efferent ducts from the anterior and aborted portion of the primitive kidney are connected with the ureter. In the Ganoi'dei and Teleostei the kidneys have the same posi- tion. The primitive kidney appears to be considerably increased in size, while the efferent ducts are not so completely differentiated as in the Selachii, where they were the cause of much complication; in th
Elements of comparative anatomy (1878) Elements of comparative anatomy elementsofcompar00gege Year: 1878 EXCRETORY ORGANS OF VERTEBRATA. 605 which, however, several ureters may open separately. In the females, also, the efferent ducts from the anterior and aborted portion of the primitive kidney are connected with the ureter. In the Ganoi'dei and Teleostei the kidneys have the same posi- tion. The primitive kidney appears to be considerably increased in size, while the efferent ducts are not so completely differentiated as in the Selachii, where they were the cause of much complication; in the Ganoi'dei, however, the presence of a nephrostome, with a wide abdominal orifice on the efferent duct, speaks to the commencement of the process by which the Mullerian duct is differentiated; the ureter, therefore, no longer corresponds to the archinephric duct. In the Teleostei the secondary portion of the gland first appears on the anterior division of the archinephric duct, and forms that portion which, in many, extends as far as the head (head-kidney). The hinder portion, which is developed later, becomes connected with this. The whole forms a compact glandular organ, which is covered by the peritoneum, and extends along the vertebral column; it varies in size in different regions. Its differentiation into lobes is generally implied by the greater development of certain regions. The efferent ducts (Fig. 345, u) either pass along the anterior surface, or more to the sides ; they generally unite into an unpaired portion, which opens behind, or below the generative orifice. The ducts are widened at different points, either in the common, or in the separate portions; these struc- tures function as ' urinary bladders,' but they have no morphological connection with the urinary bladder of the higher Vertebrata. The renal organs of the Amphibia have many points in common with those of the Selachii. The rudimentary ducts are always provided with func- tionally active nephrostomat
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