Foetal Membranes of the American Beaver (Castor canadensis). 



207 



from the line of insertion of the vascular clioriou 1 ), i. e. below the 

 level of the sinus terminalis (Fig. H). 



Over this narrow interval the surface appears granulated when 

 examinad with a lens. being covered with low elevations flattened 

 from above. Here and there on the general surface, a villus is found 

 presenting a turgid. vesicular or inflated structure, suggesting that 

 all the villi might be capable of similar dilatation intra vitam; 

 or it may be merely a post mortem appearance. 



Fig. J. 



Foetal beaver iii its amnion suspended back downwards from tbe placenta; seen 

 after ablation of tbe chorion, pieces of wbich are left at tbe umbilico-placental 

 insertion and at the occlusiou of the amnion, at the end of the omphalo-mesenteric 



cord. 



1. Portion of chorion, tnrned aside. 2. Placenta. 3. Utero-placental vessel. 4. Point 



where the amnion meets the placenta. 5. Amnion. 6. Omphalo-mesenteric ligament, 



seen through the amnion. 7. Portion of chorion. 8. Omphalo-mesenteric cord. 



9. Umbilical cord. 10. Amnio-placental insertion. 



1) The vascular chorion of the mature Rodent blastocyst is the 

 Tunica quarta seu erythroidalis of Needham. Tunica ery- 

 throidalis might well be adopted as a distinctive name for it. Endo- 

 chorion (Dutrochet) and Endochorionic villi would also be suitable terms. 



