282 



Dr. M. Watson. 



of course correspond to the central point of the placenta, inasmuch 

 as at this point the separation of the true from the false amnion takes 

 place. The close attachment of the true amnion to this point, as well 

 as the fact that the continuity of the allantois over the junction of 

 what originally was the false with the true amnion, could be clearly 

 traced in Procyon, lends additional support to this view ; while, at the 

 same time, it strengthens the interpretation above given of the mor- 

 phological significance of the sac in question. 



The Foetus. 



Upon removing the foetus from the uterus, the former was seen to be 

 completely invested by an opaque membrane of a bluish colour. This 

 membrane, to which the name of epitrichium has been given by 

 Welcker,* formed, as it were, a second or supernumerary cuticle to 

 the foetus, and was closely applied to every part of it. Over the 

 greater part of the foetus it lay superficial to and concealed the hair 

 with which the embryo was covered. At some places, however, and more 

 especially over the inter- scapular region, the forehead, and the outer 

 sides of the thighs, the free extremities of the subjacent hairs projected 

 through this membrane, as did also the large vibrissas surrounding 

 the mouth. The membrane was thinner and more closely adherent to 

 the head, the distal half of the tail, and to the legs below the knee and 

 elbow joints, than elsewhere, and could not be removed from these 

 parts without tearing; whereas, from the other parts of the body, where 

 the membrane was of greater thickness, it could readily be detached 

 as an entire structure. The membrane agreed in all respects with 

 the epitrichium described by Professor Turner in the two-toed sloth 

 (Cholcepus Hoffmanni) ,f except that in the latter, with the exception of 

 the tactile vibrissa? of the snout, none of the hairs protruded through 

 this membrane ; whereas in Procyon numbers of the hairs of other parts 

 of the body pierced it. As in Cholcepus Hoffmanni, so in Procyon, the 

 epitrichium was continuous with the mucous membrane of the ears, 

 eyes, mouth, and anus. An examination of the deeper surface of the 

 membrane disclosed a punctated and irregular appearance of the latter. 

 This was doubtless due to the impact of the growing hairs. A similar 

 appearance was met with by Professor Turner in the deeper surface of 

 the epitrichium of the sloth. Under the action of caustic soda, the 

 membrane resolved itself into numerous flattened epithelial scales, in 

 which at times distinct nuclei were visible. These scales differed from 

 those described by Professor Turner in the sloth, % inasmuch as their 

 edges were uniformly smooth, and presented no trace of the inter- 

 locking processes described by that anatomist. 



* " Abhandkmgen der Naturforsch. Gresellschaft," Halle, Band x, p. 20. 

 f " Trans. Roy. Soc. Edin.," vol. xxvii, p. 71. 

 X Ibid., p. 71. 



