1153 PR01<\ J. p. HILL AND MR. R, H. BURNE ON THE 



lining endothelium. The vein (fig. 14, umh.v.) is empty, and its 

 wall lacks the compact zone of muscle and appears contracted 

 and its lining folded. 



Epithelial pearls occur below the am^niotic investment of the 

 cord in the region of its junction with the allantoic sac, and are 

 probably derived from the amniotic epithelium, since they are 

 also occasionally found below the amnion covering the inner wall 

 of the allantois adjacent to the cord-junction. 



From the junctional region, branches of the umbilical vessels 

 pass off to run in the inner wall of the main allantoic sac. Some 

 of these after a short coui\se i-each the allanto-chorionic con- 

 nective tissue directly in specimen B, by way of three septal 

 pillars (figs. 13 & 14, sept.) which extend obliquely across the 

 lumen of the main sac between its inner and outer walls, as 

 Strahl appears to have observed in Galar/o (14, p. 182). In 

 specimen A, these septa a.ppear to be absent. Other branches 

 after a straight or slightly branched course reach the allanto- 

 chorion by passing round the maigin of the main sac. They are 

 seen emerging in PI. II. figs. 2 & 3 a,nd text-figs. 2 & 3 in the angles 

 of the clefts between the main and accessory lobes. Yet other 

 branches run straight on from the inner wall of the main sac to 

 supply those regions of the chorion that are not underlain by 

 prolongations of the allantois. In the chorionic connective 

 tissue, the vessels subdivide and run in all directions to supply 

 the subtrophoblastic capillary plexus of the laminar villi. 



Both Milne Edwards (3) and Anthony (12) state that the 

 allantoic walls in the Lemurs examined by them are devoid of 

 blood-vessels. That, of course, is an erroneous statement as 

 applied to the allantois as a whole, but it is partially true of the 

 accessory lobes, since the inner walls of these (remarkably delicate 

 and thin, as Milne Edwards remarks) are quite devoid of vessels. 

 Thus it is an unexpected and somewhat remarkable fact that 

 these accessory allantoic lobes in the Lemurs are not really con- 

 cerned with the vascularization of the chorion, and the question 

 arises as to their possible significance. One of the functions of 

 the allantois is to serve as a receptacle for the urinary fluid ex- 

 creted by the mesonephroi, and it is possible that the formation 

 of these lobes is to be correlated with the presence in the foetus 

 of actively functional mesonephroi. In this connection it is 

 interesting to note that Hubrecht (11) records that in the 6-mm. 

 embiyo of Nycticehus, the glomeruli of the mesonephros are 

 remarkably large. 



Whatever may have been the inciting cause of the growth of 

 the allantois, there can be little doubt that its lobulated form is, 

 as Milne Edwards (3, p. 283) suggested, a direct result of the 

 position early assumed by the umbilical vessels on the walls of 

 the main lobe, the first formed pait of the organ. If that be 

 so, then the actual form assumed by the allantois is a secon- 

 dary matter and likely to be inconstant in its details, even in the 



