MR. OWEN ON THE GENERATION OF THE MARSUPIAL ANIMALS. 337 



brane, which here was plainly seen to terminate in a well-defined ridge, formed by 

 the trunk of a blood-vessel. 



When the whole of the vascular membrane (Plate VII. fig. 1. c.) was spread out, 

 its figure appeared to have been that of a cone, of which the apex was the umbilical 

 chord, and the base the terminal vessel above mentioned. Three vessels could be 

 distinguished diverging from the umbilical chord, and ramifying over it. Two of 

 these trunks contained coagulated blood, and were the immediate continuations of 

 the terminal or marginal vessel ; the third was smaller, empty, and evidently the 

 arterial trunk. Besides the extremely numerous ramifications dispersed over this 

 membrane, it differed from the chorion in being of a yellowish tint, which is still 

 perceptible in the preparation. No trace of any other membrane could be seen ex- 

 tending from the foetus besides the two above described, and the amnios (Plate VII. 

 fig. 1. h.), which was reflected from the umbilical chord, and formed, as usual, the 

 immediate investment of the foetus. 



The umbilical chord measured two lines in length and one in diameter. It was 

 found to contain the three vessels above mentioned, with a small loop of intestine ; 

 and from the extremity of the latter, a filamentary process was continued to the vas- 

 cular membrane. The margins of the umbilicus or abdominal opening were very 

 strong, offering much resistance to their division. On tracing the contents of the 

 chord into the abdomen, the two larger vessels with coagulated blood were found 

 to unite ; the common trunk then passed backwards beneath the duodenum, and 

 after being joined by the mesenteric vein, went to the under surface of the liver, 

 where it penetrated that viscus : this was consequently an omphalo-mesenteric or 

 vitelline vein. The third vessel passed between the convolutions of the small intestine, 

 along the mesentery, to the abdominal aorta, corresponding to an omphalo-mesenteric 

 or vitelline artery. The membrane, therefore, upon which they ramified answered to 

 the vascular layer of the germinal membrane, which spreads over the yolk in the 

 oviparous animals, or to the umbilical vesicle of the embryo of ordinary Mammalia. 

 The filamentary pedicle which connected this membrane to the intestine was given 

 off near the end of the ileum, and not continued from the caecum *, the rudiment of 

 which was very evident half a line below the origin of the pedicle. 



The small intestine above the pedicle was disposed in five folds. The first from the 

 stomach, or duodenum, curved over the vitelline vein, and the remaining folds were 

 disposed around both the vitelline vessels. From the caecum, which was given off 

 from the returning portion of the umbilical loop of intestine, the large intestine passed 

 backwards to the spine, and then, bent at a right angle, straight down to the anus. 

 The stomach did not present any appearance of the sacculated structure so remark- 

 able in the adult, but had the simple form of a carnivorous stomach. 



* The umbilical vesicle, though small, is very conspicuous in the embryo of the Porpesse when two inches 

 in length, but there is no caecum in this animal ; affording, therefore, with the Kangaroo, both negative and 

 positive proof that the caecum in Mammalia is not a remnant of the yolk-duct. 



