FEMALE ORGANS OF MAESUPIALTA. 



681 



536 



ovarium of the bird. Numerous ovisacs in different stages of 



o 



growth project from the surface, the largest presenting a diameter 

 of eicrht lines, fio\ 536, a ; but the structure of these ovisacs, the 



C5 * ~ ' 



character of the stroma in which they are imbedded, and the 

 dense albugineous tunic by which they are inclosed, bespeak 

 their strictly mammalian type. The oviducts contract, beyond the 



J if L > 



pavilion, b, to a greater 

 degree than in Mono- 



o 



tremes, and both by 



/ 



their slenderness and 

 the thickness of their 

 coats more nearly re- 

 semble the spermducts ; 

 they have, also, usually 

 a more or less tortuous 

 course, as shown in the 

 Opossum, fig. 537, and 

 Kangaroo, fig. 538, b, b. 

 Their expansion into 

 ' uteri ' is more gradual 

 than in higher Mam- 

 mals. The uteri are fusi- 

 form, relatively longer 

 in multiparous, fig. 537, 

 than in uniparous, fig. 

 538, species. The mus- 

 cular coat is of moderate 

 thickness, exceeded by 

 the innermost, owing to 

 the abundance of lax areolar and vascular tissue which supports 

 the smooth delicate lining membrane, which is usually thrown 

 into many folds. Each uterus communicates with its own vagina 

 by a valvular prominence, or ' os tinea?.' The vaginae are of 

 remarkable length in Marsupialia, and folded or otherwise deve- 

 loped, so as to adapt these passages to detain the foetus after it 

 has been expelled from the uterus for a longer period than in 

 other Mammalia. 



These complications vary considerably in the different mar- 

 supial genera. On a comparison of the female organs in Didti- 

 phys dor sic/era, Petauruspygmceus, Petaurus taguanoides,Dasyurus 

 viverrinus ; Didelphys Virginiana, Macropus major, and Hypsi- 

 prymnus murinus, I find that the relative capacity which the 

 uteri bear to the vaginae diminishes in the order in which the 



Ovariuui and ravilion, "Wombat. Natural size. 



