374 Sir R, Owen on an Impregnated Uterus and 



In 1880 I was favoured by receiving a female Echidna, 

 killed August 30, 1879, in which the left uterus contained 

 three ova ; also a female Echidna, killed September 14, 1879, 

 in which one ovum was contained in the right uterus. The 

 female organs of both specimens are subjects, figs. 1 and 3, of 

 pi. xxxix. Phil. Trans. 1880, enlarged views being given of 

 the most advanced ovum (the natural size being 6 millim. in 

 diameter) in figs. 2, 4, and 5 of the same plate. A magnified 

 view of a portion of the outer tunic (" hyalinion ") of the ovum 

 is given in fig. 3. This tunic was thin, smooth, without 

 trace of vascularity, and the sole indication of commencing 

 development was a linear indentation of the vitelline mem- 

 brane of the single ovum. 



Continuing the correspondence with my coadjutor in this 

 quest, I subsequently received the female organs, preserved 

 in alcohol, of an Echidna, captured in the month of September, 

 1882, in the vicinity of Toowoomba. The increased size of 

 both uteri led me to hope for more decided testimony on the 

 moot question of the oviparity or ovo-viviparity of the Mono- 

 tremes. 



The right uterus was laid open and a collapsed ovum was 

 exposed ; an accomplished artist was engaged to make the 

 drawing (PI. XIII. fig. 1) before proceeding further with the 

 quest. This being completed I laid open the left uterus by 

 a similar longitudinal incision, and exposed a still more col- 

 lapsed ovum \ih. fig. 2,g'). 



In both uteri the absence of any connexion of the ova with 

 the uterine walls was shown by their floating freely as moved 

 by the feeble wave of the menstruum in which the dissection 

 was made. The vitelline mass, exposed by the section of 

 the outer tunic, had assumed a similar elongate figure {h', 

 fig. 2). 



The flattened ovum, f, of the right uterus was then re- 

 moved, and the vitelline mass exposed, as in fig. 3. A linear 

 indent of the vitelline membrane, h, seemed to repeat that 

 noted in the smaller ovum of the specimen previously (1880) 

 described. The chief change, besides increase of size, was the 

 increased thickness of the smooth tough outer tunic (" cho- 

 rion " or " hyalinion "j, in which as little trace of vascu- 

 larity was present as in the ovum at the earlier period of 

 its uterine existence. I concluded therefore that the unde- 

 veloped ovum would have been excluded as such ; and the 

 confirmation of this view is given in an Australian periodical 

 with which I was subsequently favoured. 



In the ' South Australian Register ' of September 8, 1884, 

 the Director of the South Australian Museum, Adelaide, J. W. 



