ON THE ARRANGEMENT OF THE FCETAL MEMBRANES IN THE CETACEA. 501 



he says, the typical form of the glandular organ is wanting, but the cells of the 

 serotina, which invest the chorionic villi, represent the fundamental portions of 

 the gland organ. Into these new-formed secreting follicles, and not into the 

 utricular glands, the villi of the chorion penetrate, and are bathed by the fluid 

 secretion, which they absorb for the nourishment of the foetus. He believes 

 that these observations completely overthrow the view so frequently enter- 

 tained that the nutrition of the foetus is due to an exchange of materials by 

 processes of exosmosis and endosmosis between the two vascular systems. 



There can be no doubt that the structures which I have described, both in 

 Orca and in the mare, as the crypts of the mucous membrane, are the same as 

 those to which Ercolani gives the name of follicles. I have already discussed 

 the probable mode of formation of these structures, and whilst considering that 

 the deeper, funnel-shaped crypts'" may, from their relation to the glands, be 

 regarded as their dilated mouths, yet I have inclined to the view that the cup- 

 shaped crypts are pouches formed during gestation by the folding of the surface 

 of the greatly hypertrophied mucous membrane. Hence they may be looked 

 upon as newly-formed follicles ; and, so far, I agree with Ercolani. 



Are they, however, to be regarding as secreting ? Here I experience 

 greater difficulty in accepting Ercolani's theory ; for although their epithelial 

 lining is anatomically continuous with that of the utricular glands, yet it is 

 not of the same character. Both in Orca and in the mare, whilst the glan- 

 dular epithelium is cylindrical, that lining the crypts is pavement. Now, we 

 are not in the habit of regarding the pavement epithelium as secreting in its 

 functions, for in the localities where it is customarily found, it seems to fulfil 

 merely a protective office, whilst the function of secretion is reserved for cylin- 

 drical, spheroidal, or polygonal epithelial cells. 



Again, I am not disposed to consider that the utricular glands cease to 

 perform their functions at an early period of embryo-life. In this Orca, 

 although the foetus had reached an advanced stage of development, the vascularity 

 of the glands, their epithelial contents, even the presence of plugs of epithelium 

 or inspissated secretion projecting through their orifices, all gave one the impres- 

 sion of structures in a state of active employment. If this be the case, then 

 the secretion would be poured out into the crypts, and brought in contact 

 with the villi of the chorion. In the mare, however (and it is quite possible 

 also in Orca, although I have as yet no positive observations), some of the 



* It may be said, as an objection to the inference that the funnel-shaped crypts are the dilated 

 mouths of glands, that in the mare some of the utricular glands open on the surface by circular 

 orifices without exhibiting any dilatation, and that therefore the crypts into which the glands open are, 

 like the other crypts, merely due to a folding of the mucous membrane at that spot. The difference 

 in the character of the epithelial lining of the glands and crypts, and the similarity in the epithelial 

 lining of all the crypts, may also be advanced as additional reasons why all the crypts should be 

 regarded as formed after the same plan, and not by the dilatation of gland orifices. 



