ZOOLOGY. 555 



ureters usually unite into a large urinary bladder. Thus, 

 the sexual lung is also significantly developed. 



3372. Many of these urinary bladders split, as in the 

 Tortoises, into two cornua. This is the form under 

 which the bladder again occurs in Birds, where its two 

 cornua have been incorrectly termed cceea, but the uri- 

 nary bladder rectum, because the intestine opens into it. 



3373. In Reptiles also there is a cloaca or sexual 

 orifice, into which all the sexual apertures meet together. 



The ova of Reptiles possess a vitellus and albumen, 

 and are surrounded by a membranous or sometimes by 

 a calcareous shell. 



3374. Hence Reptiles have originally also a co3cum, 

 but it has for the most part disappeared ; like its antetype 

 the vitelline canal, which is so small in most Fishes and 

 Birds, as to be scarcely distinguishable. 



The tail projects from the body, and is rather trailed 

 after the animal, than enabled to assist the body in its 

 motions, as in "Pishes. 



Senses. 



3375. Many Fishes have only a vertebral column with- 

 out lateral bones ; in the Thoracic animals this deficiency 

 can hardly occur any longer, although we are not, on the 

 other hand, to expect any great amount of perfection to 

 be attained by these parts. Reptiles have osseous 

 ramules, whether such be ribs or true feet ; the Serpents 

 have indeed only ribs, but these exist in great numbers ; 

 in the Frogs, on the contrary, ribs are wanting, but they 

 have limbs. 



In no Reptile do fin-rays occur ; consequently, there 

 are no peculiar bones as in Fishes. 



3376. In Reptiles the limbs themselves are in a varied 

 or undetermined state, although they constitute a class 

 in which the formation of true muscular limbs is decided. 

 In Reptiles the toes appear for the first time. 



3377. As regards the tegument, it quite corresponds 

 with that of the Corals, Snails, and Crabs, of which the 

 Reptiles are a repetition. In some cases it is slimy and 



