726 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Placenta of Inuus nemestrinus.* — Prof. W. Waldeyer is able to con- 

 firm Turner's statement as to the resemblance of the human and simious 

 placenta ; the spongy layer of Inuus is more like that of Homo than is 

 that of Macacus. A continuous layer of endothelium is found on the 

 placental surface of the decidua, and passes on one side into the foetal 

 villi, and on the other into the maternal placental vessels. The author 

 shows that the chorion and villi have a double cellular investment, and 

 that the blood in the intervillous spaces is of a normal character. 



Placentation of the Dugong.-j- —Prof. Sir William Turner has had 

 the opportunity of examining the placenta of the Dugong, and has added 

 to, and in some points corrected, the observations of Harting, who stated 

 that the placenta was diffused and non-deciduate. The author finds that 

 should the placenta be non-deciduate, in the sense that the vascular 

 part of the maternal mucoiis membrane is not shed, the placenta of the 

 Dugong gives a new type, one which is both zonary and generally non- 

 deciduate. The diffused character of the placenta in the specimen 

 described by Harting was due to its comparatively early stage of deve- 

 lopment, for the villi had not as yet limited themselves to a definite zone. 



Development of Placenta in Dog.| — Dr. G. Heinricius gives an 

 account of the growth of the placenta in the dog. The uterine mucous 

 membrane includes two kinds of tubular glands — superficial crypts and 

 long glands reaching to the muscular layer. With the entrance of the 

 fertilized egg into the uterus, both crypts and long glands elongate and 

 ramify. This is especially marked in the long glands which expand 

 inferiorly into cyst-like spaces. When the foetal ectoderm comes in 

 contact with the uterine wall, the epithelium of the latter degenerates, 

 and is apparently absorbed ; foetal villi grow into the connective tissue 

 septa of the crypt-stratum ; then the epithelial layer of crypts and glands 

 also degenerates, and the villi come to be surrounded by a syncytium. 

 The deep stratum of long glands remains unaltered, wlaile the upper 

 has been modified into the maternal placenta. The villi of the chorion 

 consist of a gelatinous tissue surrounded by a simple epithelium very 

 closely adherent to the maternal syncytium. Even when the embryo is 

 only 1 • 5 cm. in length, there may be seen round each pole a pair of 

 narrow zones, the " lateral blood-sinuses." When the epithelium of the 

 chorion comes into contact with these, its cells contain blood-corpuscles, 

 which suggests an important nutritive role. In the cystic enlargements 

 of the long glanas, great cellular activity sets in, " uterine milk," or 

 plasmic secretion is formed, the villi eventually reach this, and when 

 they do so, their epithelium becomes adaptively altered in order to 

 utilize the special nutritive material. 



Pro-amnion and Amnion in the Chick. §— Dr. T. W. Shore and 

 Mr. J. W. Pickering find that there is a diblastic pro-amnion in the 

 chick, of the same nature as that of mammals. It is bounded at the 

 sides by the anterior vitelline veins, and so agrees with that of mammals. 

 The sinus terminalis, unlike that of mammals, is venous. The headfold 

 is formed by the forward growth of the head over the diblastic pro- 

 amnion, and not by a folding-off from the blastoderm. The head, tail, 



* SB. K. Preuss. Akad. Wiss,, 1889, pp. 697-710. 



t Proc. R. Soc. Edinb., xvi. (1889) pp. 2(J4-5. 



X SB. K. Preuss. Akad. Wiss., 1889, pp. 111-17. 



§ Jouni. of Auat. and Physiol., xxiv. (1889) pp. 1-21 (1 pi.). 



