Chap, vii.] SAUROPSIDA ; MAMMALIA. 



261 



Cv Ao 



FK 



kidneys of the Amniota obtain in the relative position 

 of the two organs ; in Snakes, for example, not only 

 are the kidneys elongated in relation to the general 

 form of the body, but 



/ * 



one lies a good deal 

 in front of the other ; 

 this difference of 

 level between the 

 two kidneys, which 

 is clearlv an arrange- 



inent for more con- 

 venient packing, may 

 be seen also in some 

 Mammals (rabbit) ; 

 secondly, the kidneys 

 vary considerably in 

 their external form ; 

 thus, those of the 

 lizard are only 

 slightly, those of the 

 Ophidia much more, 

 broken up into lobes; 

 this is a difference, 

 also, which obtains 

 between young and 

 old forms, for in the 

 latter the number of 

 lobes is much greater 

 than in the former. 

 In Birds the lobes 

 fit into the spaces 

 between the trans- 

 verse processes of the vertebrae of the pelvic region, 

 The lobes of the kidney, after appearing, do, in many 

 Mammals, again fuse with one another, so that 

 while the Cetacea, in which this process does not 

 obtain, may have as many as two hundred lobes, the 



;. 108. Urogenital Apparatus of a Male 

 Frog. 



, Kidneys ; ur ur, ureters ; + tbeir point of 

 origin ; s s', their opening into the cloaca Cl, 

 H o, testes ; FK, fat body ; AO, aorta ; cr, 

 vena cava inferior ; vr, efferent veins. 

 (.After Wiedersheim.) 



