630 EXCRETING ORGANS. 



approximated laminae, extending longitudinally along the 

 whole extent of the abdomen, under the vertebral column, 

 and from the periphery of the organ towards the lateral 

 portion of each tube or ureter, numerous minute tor- 

 tuous tubuli uriniferi are developed to extend the se- 

 creting surface. Their structure much resembles that of 

 the corpora Wolffiana of birds, which were thought to be 

 deciduous kidneys, but the kidneys are here developed much 

 posteriorly to the situation of these remarkable deciduous 

 glands. The kidneys retain their primitive foetal condition 

 to a much later period in the tritons than in the frogs and 

 toads, and their adult form is more elongated in the perenni- 

 branchiate species, as the proteus and siren, than in those 

 which lose the gills. The closed vesicular terminations of 

 the tubuli are perceptible around the periphery of the soft 

 vascular blastema, earlier than the narrow tubular necks by 

 which they communicate with the ureters, as the develop- 

 ment proceeds from the circumference to the centre of these 

 organs, and the development of the ureters appears also to 

 proceed from their renal ends backwards to their open 

 cloacal extremities. The form of the kidneys is more 

 elongated and narrow in the ccecilia and triton than in sala- 

 mandra and the anurous species, and the urinary bladder 

 of ccecilia is bilobate in form, like that of other caduci- 

 branchiate amphibia. The urinary bladder has a simple 

 and elongated form in the species which retain the bran- 

 chiae, as the axolotuSy siren, and proteus. The tubuli 

 are unusually large in the adult pro feus. The dichotomous 

 division of the tubuli uriniferi, near their closed ends, has 

 been observed by Huschke in some of the amphibia, and 

 also vesicular peripheral terminations, which latter are gene- 

 rally confined to the earlier stages of the development of 

 the tubuli. The small round corpuscula Malpighiana turgid 

 with red blood, are already abundant and conspicuous in 

 the texture of the kidneys of amphibia, as in higher 

 classes. 



In the ophidian reptiles, as in fishes and birds, the urinary 

 bladder is very rarely developed, and the ureters terminate 

 as usual, directly and separately in the cloaca. The kidneys 

 of serpents, like most other organs of the body, partake of 

 the elongated form of the trunk; the left is situated farther 

 backwards than the right ; they are surrounded entirely with 



