014 



COMPARATIVE ANATOMY. 



commence by a wide abdominal month. The mucous membrane 

 which invests them is set in a number of longitudinal folds ; the 

 lower portion, in addition to the greater thickness of its muscular 

 wall, is distinguished from the other and longer portion by the larger 

 size of its folds and villi; this is especially the case in Birds. This 

 differentiation of the oviduct corresponds to the different function of 

 the different parts ; the longer and more anterior portion secretes the 

 albumen, and the thick- walled terminal part forms the shell. This 

 portion is connected by a short and narrower piece with the cloaca. 

 In correlation with the atrophy of the right ovary the oviduct of the 

 same side is also atrophied in Birds ; not unfrequently, however, 

 remnants of it are found near the cloaca. While the oviducts open 

 by one orifice in the Ophidii and Saurii, as well as in Birds, in the 

 Chelonii they open into the neck of the so-called urinary bladder ; 

 this foreshadows the relation which is the typical one among the 

 Mammalia. In many Ophidii a diverticulum of the posterior wall of 



the cloaca receives the openings 

 of the oviducts. A remnant of 

 the primitive kidney is retained 

 behind the ovaries (this has been 

 observed in the Saurii and Aves). 

 The testes, which are gene- 

 rally oval, are attached to the 

 vertebral column by a fold of 

 the mesenteries ; this is either 

 effected in front of, or between 

 the kidneys. Their size is closely 

 correlated with their physio- 

 logical activity ; this is especially 

 the case in Birds. In the Ophidii 

 they are arranged in the same 

 way as the ovaries. The vasa 

 efferentia pass to a parorchis, 

 which generally consists of a 

 few canals only, and from which 

 a vas deferens extends to the 

 cloaca. In the Crocodilini it 

 is straight, in the Ophidii, Saurii, 

 and Aves it is arranged in a 

 number of smaller coils, while 

 in the Chelonii (Fig. 349, e) it 

 forms a complex of coils. In 

 many Saurii arid Aves, as well 

 as in the Crocodilini, its hinder 

 portion is widened out. 



In the Saurii the vasa defe- 



rentia still unite with the ureters 



to open into the cloaca; in the Chelonii they open into a sinus uro- 



genitalis, which is formed by the neck of the urinary bladder. 



Fig. 319. Urinary and generative organs 

 of a Chelonian (Chelydra serpentina). 

 r Kidney, u Ureter, v Bladder, t Testes. 

 e Secondary testes and vas deferens. 

 ug Opening of the urogenital sinus into 

 the cloaca, cl Cloaca, opened from be- 

 hind, p Penis, s Groove of the penis, 

 re Hind gut. c c' Cloacal csecal sacs. 



