48 
THE VOYAGE OF H.M.S. CHALLENGER. 
the nervous terminations are pressed closely against each other, whilst in the living 
animals these groups are spaced as shown in the following figure : — 
Pig. 1 . — Diagrammatic representation of a part of one of the cones of Clione. a, epithelium ; b, elongated epithelial cells 
surrounding the nervous termination ( c ) ; d, longitudinal muscular fibres ; e, circular muscular fibres ; /, unicellular 
glands, the secretion of which ( g ) spreads outwards, through the elevated epithelial cells (b). 
The secretion of the glands contained in the cones serves to attach the prey of Clione, 
as has been observed by Wagner. 1 
At the base of the buccal cones the digestive tract, that is the anterior portion of the 
retracted proboscis, is contracted by two symmetrical lip-like pads, which I have called 
false lips ; they close the alimentary canal when the two halves of the cephalic hood are 
turned back, in order to uncover the buccal cones. 
The radula is shaped on the same plan as in the preceding families. There are no 
jaws. The hook-sacs, which are small in Clionopsis as in Dexiobranchsea , are here 
similar to those of Spongiobranchsea 2 
The remainder of the digestive tract (including the accessory glands) is comparable 
with that of the Pneumonodermatidse, except that the salivary glands do not exhibit the 
swelling prior to their termination observed in this latter family. The anus opens in the 
same place, but not in a cloacal depression common to it and the orifice of the kidney 
as in the preceding genera. 
Several of the visceral openings are very difficult to distinguish from the exterior in 
Clione. PI. Y. fig. 5 shows the various orifices in their relative positions. 
In addition to the diaphragm traversed by the oesophagus there is another posterior 
1 Die Wirhellosen des weissen Meeres, Bd. L p. 93. 
2 Compare PI. V. fig. 4, a, with fig. 2 on p. 19 of the systematic Report on the Gymnosomata, Zool. Chall. Exp., 
part lviii. 
