130 
THE VOYAGE OF H.M.S. CHALLENGEE. 
resemblances of the Nemertean proboscis to this organ make it more likely that the true 
homologies point in this direction rather than in the way of the ingenious theory (of the 
hypophysis cerebri) of my friend Prof. Hubrecht. 
There are twelve j^airs of scales, which are pale, rather thick, and friable, quite smooth, 
and beautifully though not regularly reticulated, the margin alone being granular (PI. 
XIX. fig. 8, and PL XVII. fig. 6). 
About twenty-three feet occur on each side, and the fieshy part of each is largely 
developed. Dorsally a wedge-shaped depression makes the base of each bifid. The 
dorsal division is wholly devoid of bristles, and forms a soft, conical, and minutely 
granular elevation. 
The ventral branch of the foot is much developed, forming a long, slightl}’ tapered 
process with a bifid tip. It bears one or two long, stiff, light amber-coloured l.)ristles, the 
appearance of the body being characteristic in this respect. The tip in most is slightly 
bent from injury (PI. XIa. fig. 7), then the bristle gradually widens dovmward to a kind 
of shoulder, after which the shaft is cylindrical. The whole to a certain extent resembles 
what the central axis of the ordinary ventral bristle is in the Polynoidse, all the processes 
l^eing absent. A single large spine occurs as a support to this region. 
In the structure of the body- wall (PL XXXI Ia. fig. 6) this form deviates from the 
ordinary type of the Polynoidse. The cuticle throughout the greater part of the section 
is indistinct, the only part where it is clearly visible being the dorsal arch, just over the 
dorsal longitudinal muscles and median line. On the other hand, the hypoderm is greatly 
developed. As in the Nemerteans, the layer consists of large areolas with fibro-granular 
meshes, when cut obliquely, or of a series of vertical spaces with intervening fibro- 
granular bands in vertical sections. Its thickness is also remarkable. 
The muscles of the body- wall are formed somewhat after the t 5 q)e of those in the 
Polynoidse, but they are less bulky, the contrast between this and such as Lepido7iotus 
squamatus being very striking. Thus there are a pair of dorsal longitudinal muscles, 
thick externally, and thin internally ; a pair of ventral longitudinal muscles, which are 
small and but slightly curved. The oblique muscles pass over the inner margin of the 
latter, and, meeting or nearly meeting in the middle line, form an arch over the nerve- 
cords. The latter are proportionally large and rounded, occupying the thickness of 
the h 5 rpoderm, with the exception of a superficial region. The large cords lie close 
together, separated only by a median raphe, and their tissue in section is more lax 
than usual. The muscles forming the arch of the foot and the dorsum are feebly 
developed. 
Granular masses were present at the bases of the feet, and probably represent the 
male elements. 
Mr. Haswell ^ mentions that Lepidonotus melanogrammus, from Broughton Islands, 
1 Proc. Linn. Soc. N. S. Wales, vol. vii. p. 284, pi. viii. fig. 13, &c. 
