6 
TRIE VOYAGE OF H.M.S. CHALLENGER. 
were either fused throughout their whole length, or merely separate at the point of 
origin. The eyes presented no peculiarities of structure. The otocysts were considerably 
larger than the eyes, and were visible in all the specimens examined as chalk-white 
points of about OT mm. in diameter. In one spec im en they were distinctly seen to 
contain about 100 otoconia of the usual appearance, the largest measuring about 
0‘013 mm. The structure of the skin, together with its peculiar phosphorescent cells 
(“ cells of Muller,” Panceri) has been already described by me. 
The bulbus pharyngeus, the mandibles, and the tongue have been already described 
by me. I made a careful examination of the number of rows of teeth in the radula of 
three individuals, and found that they were provided with eleven, fourteen, and sixteen 
respectively. Further hack, within the sheath of the radula, there were from three to five 
fully developed, and two undeveloped series. The total number of rows in the three 
individuals was therefore eighteen, twenty, and twenty-six respectively. As is 
usually the case, the oldest (most anterior) row consisted only of a single lateral 
tooth on either side of the median tooth, and this arrangement (1-1-1) seems to 
be the original form of the armature of the tongue in the young of these animals. 
The number of teeth then gradually increases to six or seven. The shape of the teeth 
was quite typical. 
With respect to the renal organ, I have nothing to add to my former description. 
The hermaphrodite glands (in the three specimens examined) were three in number. 
The ampulla of the hermaphrodite duct and the vas deferens I have already described. 
In all three specimens the penis was invaginated. Behind the middle of the organ 
there is a lateral prominence, through the wall of which was visible a strong cylindrical or 
conical organ ; behind this, again, a number of fine, whitish, densely set points. When the 
organ was opened this conical or sometimes wing-shaped prominence was seen to project 
freely into its interior. 1 With the exception of that portion behind the wing-shaped 
lateral prominence, where are developed the small cones, the cavity of the penis is smooth 
and often presents circular folds. The function of this wing-shaped prominence would 
appear to be to prevent the male organ from being introduced too far into the vagina. 
Gegenbaur, 2 however, and H. Muller, consider that it serves to fix the organ during 
copulation, and it cannot be denied that its structure 3 would fit it for this purpose. A 
portion of the mucous gland in the neighbourhood of the female genital opening, 
which is of a more yellowish colour, possibly represents the albuminiparous gland. The 
spermatheca is absent. 
1 Bergh, Malacolog Untersuch., loc. cit., pp. 227, 228, Taf. xxix. fig. 13a ; xxvii. figs. 21, 22 ; xxxi. fig. 4c ; 
xlv. figs. 1-4. 
2 Zeitschr. f. wiss. Zool., Bd. v., 1854, p. 356. 
3 Bergh, loc. cit., p. 228. 
