of the mantle, alongside but external to the pallial nerve. 

 Very fine branches are given off from these vessels all along 

 their courses, which further divide to form systems of capillary 

 spaces that are finest and most numerous near the margins. 

 Some of these capillary spaces are large enough to be injected 

 with starch mass, and I have a preparation of the mantle lobe 

 from which only the infolded ridge has been removed that was 

 dehydrated, cleared, and mounted in balsam, in which the whole 

 system of vessels can be traced. A gelatin mass not only fills the 

 spaces mentioned, but passes out between the cells so that in 

 sections it may be seen to be diffused throughout the tissue. 

 This seems to hold good for all other parts of the body with the 

 exception of the gills, in which organs the mass is more com- 

 pletely, but not entirely, confined to the blood spaces. The indi- 

 cation therefore is, that the blood spaces are not confined ves- 

 sels, and that the blood functions as both blood and lymph. 

 The posterior pallial vessel may be traced far anteriority, grad- 

 ually diminishing in size along its course. Here it finally joins 

 the anterior pallial vessel. The anterior pallial artery (fig. 13, 

 apa.) leaves the anterior aorta very near the cartilage and runs 

 directly to the anterior border of the hinge region of the mantle, 

 giving off vessels to this portion of the mantle on the way. 

 Here it branches into right and left vessels, each of which bend 

 abruptly ventrally (fig. 9, apa.) and pursues a course along the 

 anterior border of the mantle similar to that taken by the pos- 

 terior pallial artery at the other extremity of the animal. 



Along the anterior border of the mantle, near the dorsal line, 

 the vessel is rather small and slightly broken in its course. It 

 may be possible that this represents the border line between the 

 posterior and the anterior pallial arteries. There are other 

 reasons for believing that a large share of the animal is mor- 

 phologically equivalent to the posterior portions of other forms, 

 and that the anterior portion is greatly reduced. This has 

 received attention in another place. 



- Several vessels leave the anterior aorta to supply the liver and 

 stomach. Most prominent among these is a vessel which leaves 

 the aorta between the points of origin of the anterior and pos- 

 terior pallial arteries. This bends out toward the left side of 

 the liver, where, in injected specimens, it is very conspicuous, 



37 



