KIDNEYS OF REPTILES. 537 



tinct orifices.' In the Skate and Thornback each ureter terminates 

 in the neck of a short Ijifid ))Ux(l(ler : these open hj a common urethra 

 upon the cloacal papilla. The Lepidosiren has a small urinary 

 bladder situated behind the rectum and in front of the oviducts : the 

 ureters do not communicate directly with it, but terminate sepa- 

 rately on small papilla; in the oviducal compartment of the cloaca.^ 



With regard to the circulation in the kidney of those Fishes, as 

 e. g. the Plagiostomes, the Lophius, and the Lepidosiren, in which 

 the organ is best defined, the vein on the outer side of the kidney 

 which receives blood from the tail, the abdominal parietes, and the 

 generative organs has so far the aspect of a ' portal ' or inferent 

 vessel, that a second and larger vein, whose roots take their rise 

 in part from the renal substance, extends from the inner and fore- 

 part of the kidney to convey its blood to the postcaval vein. The 

 exterior vein is not, however, completely expended in the kidney, 

 but is also continued forward from the anterior end to join the 

 veins from the anterior abdominal parietes, and sometimes those 

 from the pectoral fins. In all Fishes the kidneys maintain the same 

 relations with the cardinal veins that their transitory homologues 

 the ' Wolffian bodies ' do in the embryo of higher Vertebrates. 



§ 96. Kidneys of Reptiles. — In this class the kidneys are always 

 a distinct pair, and are more circumscribed in form, and more 

 compact in structure than in Fishes ; but, as in them, the renal 

 tissue is uniform, not divided into ' cortical ' and ' medullary ' parts. 



In the Siren each kidney is a long, oval, subcompressed body, 

 tapering anteriorly to a point situated in the hind part of the 

 abdomen, dorsad of the rectum, with an entire investment of 

 peritoneum reflected upon their inner edges, where they receive 

 small arteries. The ureters enter the back pai-t of the cloaca, from 

 the fore part of which is developed a small allantoid or urinary blad- 

 der. The kidneys of Amphiuma resemble those of Sirent.^ In the 

 Meno-poma the kidneys are relatively longer, extending nearly the 

 whole length of the abdomen on each side of the vertebral bodies. 



In the Newt the kidneys are less elongate, and their forepart 

 becomes so thin and transparent that it lends itself favourably to 

 microscopical examination. The ciliated epithelium continued 

 from the uriniferous tubule, terminates abruptly shortly after 

 entering the Malpighian capsule, fig 355, ep : the basilemma 

 of the capsule, bin, beyond the termination of the ciliated 

 epithelium, appears to be unclothed : it is a homogenous, trans- 

 parent, structureless substance, perforated by the inferent and 

 cflcrent vessels, and not reflected over them. The inferent 



' CXX5VI. ^ XXXIII. pi. 27. 



