378 OSBORAT. [Vol. I. 



tions (Fig. 3). Overlying the muscular coat is the connective 

 tissue coat, which sends numerous septae into the mucous coat. 

 The latter is richly vascular, containing numerous blood-vessels, 

 some of which immediately underlie the inner layer of columnar 

 epithelium, cp (see Fig. 4, 71b). The utricular glands are 

 interspersed with numerous irregular cells, the lumina decreas- 

 ing in diameter towards the inner surface. The most remark- 

 able feature of the uterus is the production of the mucous coat 

 into numerous folds {utf, Figs. I, 3, 4), which in many cases 

 partially separate the closely crowded embryos from each other. 

 These folds contain all the glandular and vascular structures of 

 the main mucous coat. The smaller blood-vessels frequently 

 form the core of the secondary folds {lib, Fig. 4), and are thus 

 separated by a single layer of columnar cells, ep, from the yolk- 

 sac placenta. At other points the ducts of the utricular glands, 

 d, d, closely underlie the inner epithelial coat, ep. I have not 

 observed the openings of these glands. Fig. 4 represents a 

 typical secondary fold. 



The general arrangement of the embryos in the uterus is in 

 two rows facing each other, as shown in Fig. i, drawn after 

 the removal of two of the embryos. The bodies lie obliquely 

 across the long axis of the uterus, with the heads and tails of 

 opposing pairs often alternating, as shown in Fig. 2, the ven- 

 tral line being turned towards the cavity, the dorsal line towards 

 the wall of the uterus. It follows from this that the yolk-sac 

 placentae are usually turned over the back {see yp^ , yp'' , and j/^) ; 

 but this disposition is frequently altered by the fusion together 

 of the chorions of two or three embryos. As already observed, 

 the embryos are partially separated from each other, and en- 

 closed by the folds of the mucous membrane. Numerous and 

 extensive changes have taken place in the foetal membranes 

 since the mid-period of development. The proximal portion 

 of the yolk-sac is constricted into a wide flattened stalk con- 

 veying the umbilical artery and veins. The distal portion forms 

 a large circular disc, yp, bounded by the siitics terminalis, st, 

 which represents the folding double of the distal portion of the 

 yolk-sac against the subzonal membrane to form the yolk-sac 

 placenta. This disc is somewhat cup-shaped, the sinus termi- 

 nalis forming the rim. Its upper surface is thrown into a num- 

 ber of minor folds, and covered with elongated cells with 



