ON THE ARRANGEMENT OF THE FCETAL MEMBRANES IN THE CETACEA. 491 



membrane between the gland mouths presented an undulating appearance, from 

 the fossae and furrows, with their intervening ridgelets, which it possessed. 

 The vessels in this specimen were very perfectly filled with a carmine and gela- 

 tine injection, and the capillaries were seen to form a close polygonal network, 

 which was quite as abundant around the mouths of the glands as in the inter- 

 mediate parts of the membrane. 



The study of this specimen has been of great service as a guide in deter- 

 mining the signification of the appearances presented by the free surface of the 

 more complicated uterine mucous membrane in the gravid Orca. In both 

 animals it was clear that the utricular glands opened on the free surface of the 

 mucous membrane ; only, in the Orca they opened at the bottom of deep funnel- 

 shaped crypts, but in the pig, either on the plane surface or in shallow fossae. 

 In both, the gland mouths were separated by intermediate portions of mucous 

 membrane, which in the Orca was folded with so much complexity as to form 

 numerous cup-shaped crypts, but in the pig to produce only shallow fossae and 

 furrows. In both animals the mucous membrane was highly vascular, not only 

 where the glands opened, but in the intermediate portions. In Orca the villi 

 of the chorion were lodged both in the crypts into which the glands opened and in 

 the intermediate crypts ; in the pig the fossae and furrows received the highly 

 vascular transverse folds of the chorion, which represented and performed the 

 functions of the villi, and would in course of time have become villous, whilst it 

 is probable that, if the circular or star-like elevations of the chorion had been 

 developed, they would, as Von Baer has shown, have been in relation to the 

 gland orifices. It is clear, therefore, that in the pregnant uteri of these ani- 

 mals, not only the uterine glands, but the intermediate portions of mucous 

 membrane, bear important relations to the chorion. 



I have already stated, p. 477, that my observations on the mucous membrane 

 of Orca seem to justify the inference, that the deeper funnel-shaped crypts may 

 be regarded as the dilated mouths of the utricular glands which open into them. 

 But, from what I have observed in the mare, it does not appear that in this 

 animal all these glands do necessarily open, or dilate, into crypts at their mouths, 

 for some without doubt presented no such arrangement. I have said nothing 

 as yet, however, of the probable mode of formation of the cup-shaped non- 

 glandular crypts, of which two hypotheses may be advanced in explanation, one 

 to be considered here, but the other to be more appropriately discussed when 

 comparing the cetacean and carnivorous modes of placentation. 



It is well known that during pregnancy the uterine mucous membrane not 

 only becomes very vascular, but increases both in superficial area and thick- 

 ness. Many years ago, John Goodsir pointed out* that the swollen state of 



* Op. cit. p. 57. 1845. 

 VOL. XXVI. PART II. 6 M 



