Miscellaneous. 339 



present communication, and to -which I incidental!}- alhided in a 

 previous communication to the Academy *. 



The female Kangaroo in which I found the embryo was a fine 

 example of the Macropus fjiganteus, and had taken the male about 

 fourteen days before its death, which was caused by injuries 

 infiicted upon itself, due to a fright incident to the boxing the 

 animal for shipment. The embryo was therefore not more than 

 fourteen days old. On opening the uterus of the left side, which 

 was considerably swollen, the embryo Kangaroo was seen through 

 tho transparent chorion. The chorion, which was thickened in 

 places, insinuated itself between the folds into which the lining mem- 

 brane of the uterus was thrown. The chorion, however, was 

 entirely free from villi or villous processes of any kind, and was 

 perfectly separable in its entire extent from the uterine surface ; 

 indeed it was readily turned out of the uterus intact. On opening 

 the chorion, the embryo Kangaroo was seen enclosed in a very 

 delicate amnion, which was easily lacerated. "VYhat at once struck 

 me, on opening the chorion, was the large size of the umbilical 

 vesicle and the undeveloped condition of the allantois, which, 

 though small, was undoubtedly present, consisting of a pear-shaped 

 vesicle or diverticulum from the posterior part of the intestine. 

 The umbilical vesicle adhered to the chorion by that part of its 

 surface most remote from the umbilicus, the line of demarcation 

 between chorion and umbilical vesicle being indicated by a circular 

 blood-vessel. When in the fresh condition, the umbilical vesicle 

 was seen to be highly vascular. The blood-vessels that ramified 

 over its surface consisted of two veins and an artery. The veins 

 began as one vessel from the under surface of the liver, which 

 diverged at the umbilicus and united again on the umbilical vesicle 

 as a terminal or marginal vein, i. e. the circular vein just referred 

 to and which indicated the line of contact of the umbilical vesicle 

 with the chorion. The third vessel was an artery, and through the 

 mesenteric could be traced to the aorta. These vessels evidently 

 correspond to the omphalo-mesenteric or vitelline veins and arteries 

 oi other vertebrate embryos as seen, for example, in the embryo 

 chick. The disposition of the umbilical vesicle with reference to 

 the chorion (its large size and vascularity) reminded me also very 

 much of the rabbit or rodent tyije of development. AMiile, as we 

 have just seen, the umbilical vesicle was in contact with the 

 chorion, the rudimentary allantois, on the contrary, hung freely by 

 its pedicle or urachus in the space between the amnion, the stem of 

 the umbilical vesicle, and the chorion. 



When the allantois was first examined, there could be distinctly 

 seen three very fine vessels, two of which appeared to come from the 

 aorta and corresponded therefore to the umbilical or hypogastric 

 arteries of the placental mammals, while the remaining vessel I 

 considered to represent the umbilical vein of the same. The small 

 size of the allantois and the rudimentary condition of its blood- 



* " Placenta of the Elephant," Journal of Phil. Acad. toI. ^iii. p. 5. 



