Mr. A. Hancock on the Anatomy of Antiopa Spinolse. 29 



All the branches of the great posterior canal give off dendritic 

 ramuscnles, which communicate with the papillae in the same 

 manner as those from the anterior canals. The whole of the 

 ramuscules, branches and trunk canals are of a dark chocolate 

 colour when the animal is alive, resembling in this respect the 

 gland of the papillae. It is therefore likely that all these parts 

 assist in the production of the biliary fluid. The walls of the 

 canals and branches are very firm, retaining their cylindrical 

 form even when completely isolated. 



The great posterior canal has entirely escaped the notice of 

 M. Blanchard, who after describing the posterior branches of 

 the anterior trunks to be united by a transverse communication 

 in front of the anus, states that they pass down to the extremity 

 of the body*. This we have seen to be erroneous, the transverse 

 communication (PI. III. fig. 1^') being, in fact, a branch from 

 the posterior canal. He has committed this error, probably, 

 from having relied too much on the examination of living speci- 

 mens, in which many of the branches and most of the ramuscules 

 are distinctly seen through the dorsal skin. In spirit specimens 

 there is no difficulty in isolating all the principal canals, their 

 branches, and most of the ramuscules. In this way I have on 

 more than one occasion demonstrated the existence of the 

 posterior canal, and the various other ramifications of the hepatic 

 organ. I have therefore no hesitation in asserting the accuracy 

 of the above description and of the accompanying illustrations. 

 I may state, that only the terminal portion of the posterior canal 

 can be traced through the dorsal skin, the rest being concealed 

 beneath the ovary j and that this portion of it is pretty correctly 

 represented in M. Blanchard's figure, but is erroneously con- 

 nected with the branches of the anterior canals of each side. 



The hepatic gland (PI. III. fig. 1 A: & fig. 3) of the papillae is 

 very simple, being contained within an inner sheath, and extend- 

 ing almost to the apex of the papilla; it is tubular with the 

 extremity bifid (fig. 3 a), the portions being folliculated and a 

 little branched. The inner surface is lined with a brown-coloured, 

 glandular matter. 



The whole of these glands, together with the numerous den- 

 dritic branches and canals, form an exceedingly beautiful ex- 

 ample of an unravelled liver, exhibiting as it were, at a glance, 

 the complicated mechanism of this highly organized viscus. 

 These parts, however, do not appear to be the only representative 

 of the biliary organ in this animal. On each side of the lower 

 portion of the body, immediately below the skin and in contact 

 with it, there is a peculiar glandular structure composed chiefly 



* M. Delle Chiaje, who has given an account of the anatomy of Antiopa, 

 appears also to have overlooked the great posterior canal. 



