154 Mr. W. Turner on the Placentation of Hyrax. [Dec. 16, 



in which the serotina was in situ, but in others from which this membrane 

 had been peeled off. The maternal laminae w T ere covered by a layer of 

 cells, obviously continuous with the cellular lining of the crypt-like 

 recesses on the free surface of the serotina, and the laminae themselves 

 were prolongations into the placenta of the folds of the mucosa which 

 separated the crypts from each other. 



As the placenta of Hyrax, both in the form of its villi and in the mode 

 in which they are interlocked between the intraplacental maternal laminae, 

 so closely resembles that of the domestic cat, and as these laminae remain in 

 situ after the membrane, which I have named the serotina, is peeled off 

 the placenta, there can be no doubt that they are shed at the time of sepa- 

 ration of the placenta. Hence Hyrax, in its placentation, is one of the 

 Deciduata. Whether the membrane just referred to is also shed during 

 parturition is more difficult to say. The fact that it peels off the uterus 

 along with the placenta, when they are artificially separated, is not of 

 itself sufficient evidence. In the cat the whole thickness of the mucosa 

 in the placental zone peels off along with the placenta when that organ is 

 artificially separated; whilst in normal parturition the deeper part of the 

 connective tissue of the mucosa, with the remains of the blood-vessels 

 and tubular glands, persists as a covering for the muscular coat, and 

 forms a non-deciduous serotina. It may be that in Hyrax, as in the cat, 

 only the superficial part of this membrane is shed with the placenta, 

 whilst the rest remains on the zone of the uterus ; but this can only be 

 determined by the examination of a uterus immediately after par- 

 turition. 



The non-placental area of the mucosa contained tubular glands, which, 

 relatively to the extent of the membrane, were not nearly so numerous as 

 in the gravid mucosa of animals having a diffused or polycotyledonary 

 placenta. The glands were long, and the gland-stem was unbranched 

 and almost straight ; the closed end was dilated, bent on itself, and seemed 

 to give off a short branch. The secreting epithelium did not fill up the 

 tube, but left a central lumen. 



"When the chorion was cut through on either side of the placental zone, 

 the sac of the al]antois was opened into, and seen to extend up to the 

 poles of the chorion. At and close to the margin of the placenta the 

 allantois was reflected on to the outer surface of the amnion, to which it 

 obviously gave a complete investment, so that the bag of the amnion was 

 suspended in the sac of the allantois by the bands of the latter membrane 

 reflected on to its outer surface. The amnion was large relatively to 

 the sac of the allantois. The umbilical cord was short and somewhat 

 flattened. 



Numerous flattened plates, the largest of which were about T ^- inch in 

 diameter, projected from the inner surface of the amnion. They were 

 situated not only in the neighbourhood of the umbilical cord, but scat- 

 tered as far as the poles. Some were sessile, others slightly pedunculated ; 



