SIR WM. TURNER ON THE PLACENTATION OF HALICORE DTJGONG. 647 



which. I have injected, and figured in so many of the other specimens of placentae which 

 I have described.* 



Attention was then paid to the appearance of the mucous membrane lining the non- 

 fecundated cornu. The dilated commencement of this cornu was lined by a mucous 

 membrane similar in appearance to the non-placental mucosa in the gravid horn. In 

 the non-dilated part of the non-fecundated cornu, the mucous lining was partly smooth, 

 and partly elevated into slender, low, longitudinal folds. Vertical sections were then 

 made through the mucous lining of the non-expanded horn, and examined micro- 

 scopically. It was at once seen that the mucosa was much thinner than in both the 

 placental and non-placental areas of the gravid horn. The glands were cut across in 

 the sections, but the portions of gland-tube thus divided were much more closely set 

 together than in the fecundated cornu, and the interglandular connective tissue was much 

 smaller in quantity. These differences will at once be recognised by comparing fig. 6, from 

 the fecundated cornu, with fig. 9, from the non-fecundated cornu, which are drawn to the 

 same scale. The glands in the fecundated cornu were a little larger than those in the non- 

 gravid horn, but they resembled each other in the characters of their epithelial contents. 

 Whilst in both regions leucocytes, and connective tissue corpuscles were present in the 

 interglandular tissue, it seemed as if in the non-fecundated cornu the leucocytes were 

 relatively much less numerous. From a comparison of the membranes in the two cornua 

 it is obvious that the great expansion of the mucosa in the gravid horn is very little due 

 to dilatation of the glands, but is almost entirely the result of an extraordinary growth 

 of the interglandular connective tissue, which has added both to its thickness and super- 

 ficial area ; so as to accommodate it to the enormous expansion of the horn as a chamber 

 for the lodgment of the foetus, of its membranes and the fluids of the amnion and allantois. 

 The great growth of the interglandular connective tissue in the mucous lining of the 

 gravid horn in the Dugong, is in accordance with the observations which I have pre- 

 viously made and recorded on the placenta in many other mammals. 



Fcetal Membranes and Foetus. 



The chorion was an elongated sac, bent upon itself, and corresponding in form to the 

 gravid horn in which it was contained. Its left pole was in proximity to the left tuba, 

 its right pole occupied the horn where it communicated with the corpus uteri. Owing 

 to the head of the foetus being directed to the right, this pole of the chorion was more 

 capacious than the left pole near which the tail of the foetus was situated. The chorion 

 was carefully examined to see if it possessed a diverticular prolongation which had 

 occupied the dilated part of the right non-gravid horn, but none was seen. 



The outer surface of the chorion was smooth and non- villous in much the larger part 

 of its area. The villous part was limited to a zonary band, which passed around the 



* See amongst others the Placenta of the Lemurs, in Trans. Roy. Soc. Lond., vol. 166, 1876 : that of Orca 

 gladiator, in Trans. Roy. Soc. Edin., voL xxvi., 1871, and of the Grey Seal, Fox, and Cat in the same, vol. xxvii., 1875. 



