208 PROFESSOR TURNER'S ACCOUNT OF THE GREAT FINNER WHALE 



strong marginal fold, which projected for about one inch, and was thickly studded 

 with villi on its surface and free edge. (Plate VII. fig. 17.) A second fold, 

 also covered with villi, lay close and parallel to the marginal fold. Similar 

 villous covered folds of the chorion, many of which were one foot and upwards 

 in length, traversed the chorion in various parts of its extent ; frequently they 

 ran parallel to each other, and two or more were sometimes close together, but 

 at other times they were separated by intervals of 3, 4, or 5 inches. Usually 

 the greatest projection of one of these folds was about 2 inches, though some- 

 times it reached 3, or even 4, but towards their extremities they gradually sub- 

 sided to the general plane of the chorion. 



Besides these elongated folds, villous covered folds of another form, but not 

 so numerous, projected from the surface of the chorion. They were triangular 

 in shape, flattened on their surfaces, and with the apex and lateral borders 

 free. A very characteristic specimen is represented in Plate VII. fig. 18. Its 

 margin of attachment was 4 inches, whilst its diameter from this margin to the 

 free apex was 5^ inches. On the elongated and triangular folds, but more 

 especially the former, the villi were thickly studded, but on the intermediate 

 surface of the chorion they were more sparingly distributed, and were for the 

 most part collected on minute and ridge-like elevations, which intersected each 

 other, and presented an irregularly reticulated appearance. The membrane 

 between these slight ridges was comparatively smooth and transparent. 



The mucous surface of the uterus in the mother must have possessed 

 numerous depressions of considerable length and depth, into which the elongated 

 and triangular folds of the chorion would have fitted. In the special aggregation 

 of the villi on these folds an approach to the cotyledonary type of the placenta 

 found in the Ruminantia may be traced. 



The opposite surface of the chorion was in relation to the placental blood- 

 vessels, some of which were of considerable size ; one, which was measured, had 

 a circumference of 2f inches. Where the folds on the villous surface were well 

 marked an artery coursed along and gave off many collateral branches, which 

 entered into the fold to end in the villi. The chorionic vessels were surrounded 

 by a delicate connective tissue, which was loosely connected with the attached 

 surface of the amnion. Lying in this connective tissue were numerous opaque, 

 white, slender threads, which differed from the small arteries in not being tor- 

 tuous, and in giving off their branches at very acute angles. These threads 

 had to the naked eye the appearance of fine nerves. When examined with the 

 microscope, they were found to possess an external investment of well-marked 

 connective tissue, which surrounded lines of an irregular granular or semi- 

 globular substance which looked like the disintegrated medullary sheaths of 

 nerve fibres. The free surface of the amnion was smooth and glistening. 



Although nothing definite seems to be known of the period of gestation of 



