ANTIOPA. 



M. Blanchard does not appear to be aware that any such median trunk tube exists in 

 this animal; we have, however, on more than one occasion determined its presence by actual 

 dissection. 



The hepatic gland of the papillae (fig. 8) is peculiar in its structure ; it is comparatively 

 small, and lies within an inner sheath; the lower portion is narrow and tubular, the 

 termination bifid, with each division slightly branched and folliculated, forming a beautiful 

 example of glandular organisation reduced to its simplest element. Delle Chiaje has 

 . described a terminal vesicle with urticating filaments in the apex of the papillae, as in Bolts. 

 This has escaped our observation, though a distinct external orifice was visible in the living- 

 state. 



The glands of the papillae do not appear to be the only representative of the liver in this 

 genus. On each side of the lower portion of the body, immediately within the skin, there is 

 a peculiar glandular structure, composed chiefly of anastomosing tubes (fig. 1 h, A), which form 

 a network across the dorsal aspect in front of the anus. This network inosculates with the 

 minute hepatic branches leading to the papillae, and is also apparently connected with a dense 

 gland-like body («), surrounding the termination of the intestine. There can be little doubt 

 that this network of tubes is a part of the hepatic organ ; and from its internal position, it 

 points out Antiopa as one of the intermediate forms uniting the Bolidida with the other two 

 families of the order. The tongue, also, of this genus is interesting, as evincing the same fact. 



The vascular system apparently resembles that of Eolis, with the exception of some 

 variation in the disposition of the branchio-cardiac vessels. We have observed two trunk- 

 veins opening into the posterior margin of the auricle, and M. Blanchard represents several. 

 In the Bolides there is only one trunk-vein so situated ; neither is there anything like this 

 arrangement in either Doris or Tritonia. The heart is placed about the middle of the back, 

 directly below the skin ; having the intestine in front, and the ovary beneath. The ventricle 

 (fig. \j) is large and strong, the auricle {h) thin and delicate: they are contained within a 

 pericardium of great tenuity, having, lying beneath its floor, a vesicle (/), which in Boris we 

 have called a portal heart. In this instance, the vesicle opens through the lower wall of the 

 pericardium in the same manner as that does in Boris ; and, as in that genus, its internal 

 surface is plicated. We have not been able to carry the comparison further; but suppose 

 that this additional heart in Antiopa may supply the internal hepatic network with venous 

 blood, and perhaps also the glands of the papillae. 



The branchial papillae are very delicate, large, and numerous in this genus. They will 

 undoubtedly be assisted in aerating the blood by the general surface of the body. 



The cerebroid and branchial ganglia (figs. 10 a, a, b, b) are fused into one, and thus, on 

 each side of the median line, there is an elongated mass, as in Eolis ; but being more distinctly 

 bilobed, the constituent parts are easily determined. 



The pedial ganglia (c, c) are almost circular, and are placed external to, and only a little 

 below, the others. The olfactory nerves (e) are very large, and come, as usual, from the 

 upper surface of the cerebroid ganglia ; they divide into two portions, those next the median 

 line converge and go to supply the crest at the base of the dorsal tentacles ; the other 

 portions are sent to the tentacles themselves, within the base of which they terminate in 

 the olfactory ganglia (d, d). These are of a circular form. 



There is nothing peculiar in the other nerves of the supra-cesophageal ganglia, except 



