380 



COMPARATIVE ANATOMY 



which the seminal fluid passes. These organs are also represented 

 in the female, in which they are, however, much smaller. 



In Chelonians and Crocodiles the penis is single, and corre- 

 sponds to a thickened portion of the ventral wall of the cloaca 





FIG. 303. COPULATORY ORGANS OF Lacerta agilis. ( After F. Leydig.) In A they 

 are shown everted, and in B their position in the retracted condition is indicated 

 by dotted lines extending backwards from the vent (Ce). 



R, Penes ; f, spinal furrow ; SD, the so-called "femoral glands " (see p. 20). 



(Figs. 304, 305, A). It consists of fibrous and cavernous (erectile) 

 tissue, and is protrusible, being regulated by muscles. In the 

 female it is represented by a smaller clitoris. The penis bifurcates 



FIG. 304. TRANSVERSE SECTION OF THE CLOACA OF A CHELONIAN. (Slightly 

 diagrammatic. ) After Boas. 



/, fibrous body ; r, seminal furrow, bounded by cavernous tissue ; v, wall of 



cloaca. 



proximally, and its distal tongue-shaped portion ends freely ; a 

 longitudinal groove extends along the upper surface, at the proxi- 

 mal end of which the vasa deferentia open. In Crocodiles the 

 free portion is relatively longer and the groove deeper than in 

 Chelonians. 



In many Birds a copulatory organ is present, formed on a 

 similar plan to that of Chelonians and Crocodiles. It is well 

 developed amongst the Ratitae and La,mellirostres, and in many 

 other Birds can be recognised in a rudimentary condition. In 

 Struthio it resembles that of the Crocodile, and is supported by a 



