1888.] 



The Placentation of the Lemur, 



281 



A number of years ago, Professor Hermann Welcker, of Halle, 

 described by the name of Epitrichium a cuticular membrane, situated 

 superficial to the hairs, which formed a complete envelope to the 

 foetus of Bradypus tridactylus, Gholopus didactylus, Myrmecopliaga 

 didactyla, and Dicotyles. He figured it in loco both in Bradypus 

 and Dicotyles.* It was obviously quite distinct from the amnion. 



In a memoir " On the Placentation of the Sloths," published in 

 1873, I described and figured the epitrichium in Gholopus hoffmanni,f 

 and stated that I had also seen a similar arrangement in a fcetns of 

 Bradypus tridactylus. In a subseqnent dissection of the gravid uterus 

 of Bradypus tridactylus I have recognised that this membrane in its 

 relations to the foetus corresponded with Welcker's figure and descrip- 

 tion. In these animals the epitrichium formed a complete covering 

 of the foetus, and closely followed the contour of the head, trunk, 

 and limbs, immediately external to the hairy coat which was situated 

 in the interval between the epitrichium and the skin ; though the 

 epitrichium was perforated at the muzzle by the long tactile hairs 

 which grew from the lips. It was adherent to the cuticle of the 

 margins of the eyelids, of the orifice of the nose, month, external 

 auditory meatus, and anns, and was also attached to the soft cnticle 

 around the roots of the claws. It was entirely distinct from the 

 amnion, and from its relations to the hairy coat was obviously the 

 layer of the epidermis situated superficial to the hairs, and which had 

 become elevated as a distinct and continuous membrane as a result of 

 their development and growth. 



From its relation to the hairy coat, the cuticular membrane on the 

 foetus of Lemur xanthomystax was without donbt a similar structure 

 to the epitrichium investing the foetus of the Sloths, but with this 

 difference, that instead of forming a continuous envelope around the 

 head, body, and limbs of the foetus, it was broken up into flakes or 

 patches, which were the best marked where the hairs were scattered, 

 and had almost disappeared in the mature foetus, where the hairy 

 coat was thick and abundant. 



The recognition of this membrane in Lemur xanthomystax led me 

 to examine the foetus of Propithecus diadema, referred to in my 

 memoir " On the Placentation of the Lemurs," with the view of 

 seeing if a corresponding structure was present. I found on 

 immersing the foetus in water, or in spirit, that similar membranous 

 flakes floated off from the surface of the hair. In some localities 

 they were so loose as to make it difficult to say what their original 

 relation to the hairs had been, but in other places the membrane had 

 not been disturbed, and the hairs were situated between it and the 



* " Ueber die Entwicklung unci den Ban der Haut und dei* Haare bei Bradypus," 

 in ' Abhandl. der Naturforsch. Gesellschaft zu Halle/ vol. 9, 1864. 

 f ' Edinburgh Roy. Soc. Trans./ vol. 27. 



