MALE ORGANS OF MONOTREMES. 



643 



versely disposed convolutions of which, f 9 form the rest of the epi- 

 didymis: at its lower part the tube naturally untwists, and increas- 

 ing in size, ib. g, i, becomes the spermduct or ( vas deferens,' k. 

 In Man and many lower Mammals another feature of the spermo- 

 genous tract is commonly shown in the epididymis by the offset 

 and blind termination of one or more tubules, as at h, fig. 501. 



The epididymis varies in relative size and position to the testis 

 in different Mammals. In all, the semen is conducted, in coitu, 

 by a single intromittent organ traversed by a complete canal, 

 which may bifurcate at its termination in the lowest members 

 of the class. Accessory secretions are added to the semen at the 

 beginning of the urethro-seminal canal, by glands called 6 vesi- 

 cular,' ' prostatic,' and ' Cowperian.' But these do not coexist in 

 every species, and the varieties in regard to their presence and 

 development, as well as in the 

 structure and muscles of the 

 intromittent organ, are the chief 

 elements in the comparative an- 

 atomy of the Mammalian male 

 generative organs. 



§ 369. In Monotremata* — 

 These are true 'testiconda:' each 

 testicle, fig. 502, e, e } is situated 

 immediately below, or sacrad of, 

 the kidney, ib. a, and is sus- 

 pended to that gland by a fold 

 of peritoneum ; the same fold is 

 continued to the neck of the 

 bladder, inclosing the vas de- 

 ferens, fig. 308, a 9 which appears 

 to be thick and simple, but 

 when injected and dissected, as at 

 f 9 fig. 502, is seen to be slender 

 and disposed in a series of close 

 transverse folds. In neither 

 Ornithorhynchus nor Echidna 

 is there any disparity of size between the right and left testicle. 

 The vas deferens emerges from the upper and inner part of 

 the testis e; and, from the peculiar extent of its transversely 

 folded disposition, seems to prolong the epididymis nearly to the 

 neck of the bladder ; the folds gradually diminish, and the duct 

 itself enlarges, as it approaches its papillary termination, which is in 

 the beginning of the urogenital canal, y. This canal is continued 



Male organs, Ornithorhynchus. LxxXt'. 



