Messrs. Hancock and Embleton on the Anatomi/ of ^olis. 101 



on account of the great difficulty of injecting such small animals, 

 and from a feeling of the unsatisfactory nature of such an ope- 

 ration on tubes so delicate as the minute branches we have ob- 

 served. The existence however of intervisceral lacunae we do not 

 wish to deny, since the valuable papers of M. Milne Edwards in 

 the 'Annales des Sciences Naturelles^ seem to establish the fact 

 of their presence in nearly the whole of the Mollusca. 



The branches of veins coming from the skin, represented in 

 PI. IV. fig. 2 ssss, have been several times verified ; from four 

 to six venous branches have been made out, uniting so as to fortn 

 two large trunk-veins, fig. 2ppp' p' and fig. 4eeeV, on each 

 side, which joining together pour their united contents at once 

 into the auricle : one of these veins can be seen along the inner 

 aspect of the skin as far forwards as opposite to the transverse 

 portion of the intestine, receiving branches, fig. 4< gg gg, in its 

 course from the skin, into which its most advanced branch pene- 

 trates ; the other and much smaller vein turns backwards, and 

 enters the skin sooner than the former, after visibly receiving a 

 small branch or two from it. Entering the posterior part of the 

 auricle is the posterior trunk-vein, fig. 2 q and fig. 4 d, which 

 coming from the back part of the skin receives three pairs of 

 branches at least : one pair appeared coming from below as if 

 from the ovary, but was not so distinctly made out as the rest. 



If we attempt to trace the veins into the skin, we find that they 

 communicate with a system of sinuses therein. This network of 

 sinuses pervades the whole of the skin, being abundant on the 

 sides under the bases of the papillae, and on the foot, and w^e 

 suppose communicates freely with the system of intervisceral 

 lacunae pointed out by Milne Edwards. Whether the lacunae of 

 the skin have any thing like a symmetrical arrangement as prin- 

 cipal trunks or canals, we have not been able to determine ; but 

 if a cross section of a papilla be made, a distinct canal becomes 

 visible at each extremity of the section, as shown in fig. 6 c c, 

 and from this and the symmetrical order of the venous trunks 

 passing from the skin to the auricle, we might infer that such an 

 arrangement exists. Those canals run the whole length of the 

 papilla, and communicate with the meshes of a delicate cellular 

 tissue which lines the skin of that organ ; at the base of the papilla, 

 they open into the sinuses of the skin. The position of these 

 canals in the papillae, and the cellular tissue in connexion with 

 them, are indicated in PI. IV. fig. 9 of our former paper on the 

 digestive system. 



The general course of the blood will be necessarily then from 

 the ventricle along the arteries to the viscera and to the skin ; 

 in the first case it passes from the arteries, in a way we do not 

 understand, into the lacunae among the viscera and between them 



