286 PHILOSOPHY OF ZOOLOGY. 



form of an elongated bag, with large cells on the walls. 

 This bag lies in the cavity of the abdomen. 



The kidneys are lengthened and lobulated. The ureters 

 terminate usually by a single orifice in the cloaca, in the 

 form of a papilla directed towards the bag, which may 

 be considered as the bladder of urine. This bladder is 

 formed by a fold of the coats of the intestine ; it receives 

 the contents of the ureters, unmixed with the faeces. 



In this receptacle the urine frequently becomes inspis- 

 sated, and is voided in lumps at distant intervals, which 

 have frequently been mistaken for faeces. In its ordinary 

 state, Dr John Davy, to whom the public is indebted for 

 several valuable observations on the urinary organs of the 

 amphibia *, describes it as of a butyraceous consistence, be- 

 coming hard, like chalk, by exposure to the air, and con- 

 sisting of pure uric acid. 



The reproductive organs of serpents present few pecu- 

 liarities. The external organs of the male are double, each 

 short, and surrounded with bristles. These, in the rattle- 

 snake and viper are bifid, and beset with bristles. They ap- 

 pear in a pouch near the anus. In the female, the external 

 openings are double, corresponding with the condition of 

 the male organs. Impregnation takes place internally. 

 Some species are oviparous, others are ovoviviparous. The 

 young do not undergo any remarkable metamorphosis. 



Serpents are found in the greatest numbers, both in re- 

 ference to species and individuals, in tropical countries. In 

 such regions, likewise, they attain the largest size. Few 

 species are found in the temperate and colder districts. In 

 all cases they seem greatly invigorated by heat, and in its 

 absence, speedily sink into a torpid state. 



Phil. Trans. 1818, p. 304. 



