FCETAL MKMBRANES OF CHIROMYS MADAGASCARIENSIS. 1155 



of the foetus, and leaving the amnion extends into and fills the 

 choiionic appendage that lies within the unoccupied right horn 

 of the uteru!<. Turner (6, p. 577) states that in L. rufijjes the 

 allantois does not extend into " the short diverticulum of the 

 chorion which occupies the non-gravid horn." In specimen B 

 we find a similar conditio!!. The terminal process of the lobule 

 extended to the mouth of the chorionic appendage and fitted 

 closely within its lip, but did not project further into its cavity. 



From the ventro- caudal margin of the main cavity arises a 

 lobe (e) that curves round the ventral surface of the caudal end 

 of the foetus, covering the root of the tail and the right hind limb 

 and reaching to within a short distance of the free margins of 

 l©bes a and h. 



Upon the right side of the foetus (PI. II. fig. 3 and text-fig. 3) 

 the main cavity gives off from its dorsal border two lobes (/and g) 

 that pass towards the dorsal mid-line across the lumbar and 

 thoracic regions of the foetus. The caudal of these extends rather 

 more than half-way towards the mid-line of the back ; the other 

 {g) is a larger, sausage-shaped sac, that dilates gradually from a 

 comparatively narrow origin to a bluntly rounded extremity and 

 terminates upon the back of the foetus in contact with lobe d, at 

 the point at which the latter leaves the amnion to enter the 

 appendage of the chorion. 



Apart from the narrowness of the commencement of this lobe, 

 there is no indication in the allantois of the pedunculated sub- 

 sidiary lobes mentioned by Milne Edwards (3) as occurring in 

 Proplthecus. 



The umbilical cord was exposed in specimen B (Bl. III. fig. 6). 

 It measured 4*3 cm. in length, and at its emergence' from the 

 body of the foetus was subcylindrical. At about the middle of its 

 length it became more flattened, appearing as a ribbon-like band, 

 some 6 mm. in width, bordered on each side by a thinner 

 selvage. It joined the inner wall of the main allantoic lobe over 

 the right latero-dorsal surface of the foetus, running, attached to 

 the wall, for a distance of about 1'5 cm. before finally dis- 

 appearing. In specimen A, the cord passed to the left side of 

 the foetus to reach the main lobe. 



The cord (PL V. figs. 13, itinh.c., & 14) consists of a connective- 

 tissue matrix, in which are situated the allantoic canal and the 

 umbilical vessels. It is invested by the amnion, the epithelial 

 layer of which is quite thin, resembling in places a cuticular mem- 

 brane, and below this is a thin layer of connective tissue, rich in 

 cells and not everywhere clearly marked oflf from the connective 

 tissue of the cord. The allantoic canal {aU.caii.), situated between 

 the vessels, possesses a wide lumen, lined by a two-layered epithe- 

 lium of the transitional type. There are three umbilical vessels, 

 two arteries, and one vein. The two arteries (PI. V. fig 14, 

 wmb.art.) contain blood, and their walls are histologically similar, 

 each possessing a compact zone of smooth muscle just outside the 



