1865.] Prof. Owen on the Echidna Hystrix. 109 



in the Ornithorhynchus paradoxus : three ovisacs were developed and 

 attached, as in the left ovarium ; and there was also a compressed ovisac, 

 similar in size and shape to that in the left side, and exhibiting an apical 

 cicatrix, whence it is to be inferred that, in this instance, the right as 

 well as the left ovarium had furnished an impregnated ovum ; and the near 

 equality of size and close similarity of structure and condition of the right 

 oviduct and uterus equally indicated that they had participated in the 

 functions of the last season of generation. 



The urinary bladder opened into the middle of the fundus of the uro- 

 genital compartment, the uterine orifices intervening between the vesical 

 one and the ureters, as in the Ornithorhynchus paradoxus. The uro- 

 genital canal is 1 inch 4 lines in length, and about 9 lines in diameter ; its 

 inner surface shows by some coarse wavy longitudinal rugae its capacity 

 for dilatation. The rectum was here of great width ; it terminated by a 

 contracted puckered aperture in the back part of the beginning of the 

 vestibule, behind the aperture of communication of the urogenital with the 

 vestibular canal. The distal half of the vestibule is lined by a denser and 

 less vascular epithelium than the proximal one. The author concludes, 

 from these appearances, that the present Echidna had produced two young, 

 of which only one was secured, and that probably she had a mammary 

 foetus in each pouch prior to her capture. 



The one which was secured resembled the young of the Ornithorhynchus 

 in the general shape and curvature of the body, and also resembled the 

 new-born young of the Kangaroo in the proportions of the limbs to the 

 body, in the inferior size of the hind pair, in the degree of development of 

 the digits, especially of the fore pair, and in the feeble indication of eyes 

 or eyelids. But the mouth is proportionally wider, and has the form of a 

 transverse slit ; it is not circular. Upon the upper Jip, in the mid line 

 between the two nostrils, is a small protuberance corresponding to that in 

 the young of the Ornithorhynchus paradoxus, which had been covered by 

 some epidermal production. The traces of ears are less conspicuous than 

 in the young Kangaroo, the conch being little, if at all, developed in the 

 mature Echidna. 



The tail is much shorter than in the young Kangaroo, and shows as 

 much proportional size as in the full-grown Echidna, in which it is a mere 

 stump concealed by the quills and hair. 



The head is proportionally longer and more slender in the marsupial 

 foetus of the Echidna than in that of the Ornithorhynchus or of the Kan- 

 garoo, and already at this early period foreshows the characteristic elon- 

 gation and attenuation of that part in the mature animal. The form of 

 the mouth, as a transverse slit, is a good monotrematous character of the 

 young at that period, since, in all true or teated marsupials, the mouth of 

 the mammary foetus has a peculiar circular and tubular shape. A scarcely 

 visible linear cicatrix at the middle of the lower part of the abdomen is the 

 sole trace of umbilicus. 



K2 



