A 



B 



FIG. 305. DIAGRAMMATIC LONGITUDINAL SECTIONS OF THE POSTERIOR PART OF 

 THE RECTUM, THE CLOACA, AND THE COPULATORY ORGANS OF VARIOUS 

 VERTEBRATES. (After Boas.) The position of the ureter and vas deferens 

 are indicated, although not situated in the median line. 



A, Crocodile ; B, hypothetical form between A and C ; C, Monotreme (penis 



extruded) ; D, Monotreme (penis retracted). 

 bi, connective- tissue ; bl, urinary bladder ; cl, cloaca ; d, rectum ; /, fibrous body 



(corpora cavernosa of human anatomy) ; ps, sheath of penis ; ps l , aperture of 



the sheath ; r, seminal furrow or tube (penial urethra) ; s, vas deferens ; u, 



urinogenital canal. 



