300 PROFESSOR TURNER ON THE 
chorion, which are lodged in these crypts, acquire not only a considerable 
length, but a highly arborescent form, and give origin to multitudes of villous 
tufts. As the branching and growth of the villi proceed in the course of 
development, the crypts will necessarily become divided into smaller compart- 
ments; and as the villous tufts increase in number and size, the walls of the 
crypts will become, no doubt, thinned, until at length they will lose their 
uniformly continuous surface, and become subdivided into the reticulated 
arrangement described in this memoir, in the meshes of the network of which 
the villous tufts are lodged. That the increased area of the uterine mucosa 
during pregnancy is due to a great increase in the interglandular part of the 
membrane, is proved by the much wider separation of the glands seen in both 
the non-placental and placental areas of the uterus of H. gryphus, as com- 
pared with the non-gravid uterus. 
Neither in the true Carnivora nor in the Pinnepedia do the utricular glands 
appear to play an important part in fcetal nutrition in the fully formed 
placenta. Not only is the number of glands small in relation to the size of 
the placental area, but their epithelial lining has obviously undergone changes 
which do not seem to be consistent with the possession of functional vigour. 
In the cat, indeed, the lumen of the gland tube seems to be quite occluded. 
But whilst these changes have taken place in the utricular glands, other cells 
have been developed in the gravid mucous membrane, which have all the 
characters of functionally active structures. I refer to the columnar epithelium 
cells lining the crypts, and investing the free surface of the lamine and 
trabecule, with which the chorionic villi are in opposition. On the theory 
that the walls of the crypts, the lamine, and trabecule, are produced by a 
great growth of the interglandular part of the mucosa, these cells would be 
descended from the epithelial covering of the non-gravid mucous membrane. 
Professor ERcoLANI, who has described the arrangement in the cat, considers 
that by the great growth and folding of the mucous membrane during pregnancy, 
multitudes of glandular follicles (crypts) are formed, of which these cells are the 
ephithelial lining ; and there can be no doubt that the same conclusion must 
be come to respecting the similar cells which I have found in the placenta 
of the bitch, the fox, and the seal. The crypts or follicles are therefore to be 
regarded as secreting structures, which in the Pinnepedia and Carnivora have 
replaced the utricular glands. From the maternal blood-vessels which lie 
immediately subjacent to this epithelial layer the cells elaborate a secretion to 
be poured into the follicles or crypts, where it is absorbed by the villi, and 
applied to the nutrition of the foetus. It would appear, therefore, as has 
been suggested by Erconant, that in these and in all other mammals in which 
a similar glandular organ is produced, the nutrition of the foetus is effected, 
not by a direct interchange of materials between the maternal and feetal 

