38 
THE VOYAGE OF H.M.S. CHALLENGER. 
are rather flattened. The second papilla is rather smaller than the first, but otherwise 
just like it ; the left hand organ is also prolonged but into only two finger-like processes, 
and has on the inside a large posterior, and a small anterior branchia. The third papilla 
is smaller still, and is prolonged into one or two thick finger-like processes above, with the 
usual two branchise on the outside, but only one on the inside. The fourth papilla is 
rather low (4 ‘5 mm. high), ending above in two points, with one branchia on the inside 
(unprovided with a cirrus). The fifth papilla is lower still, and prolonged above into a 
simple or slightly forked extremity ; on the outer side of the right hand one is a small 
branchia with a cirrus, which is absent from the left hand branchia. The short tail 
(3 mm. long) has a high keel, ending in a point above about as high as the length 
of the tail. — The sides of the body are high, but decrease in height from the level of 
the third papilla backwards ; a little below the anterior margin of the first papilla on the 
right is the eyelet-like wrinkled genital aperture. — The foot is rather narrow, slightly 
broader in front than elsewhere ; from the region of the third papilla backwards it rapidly 
narrows ; the marginal brim is about 3 mm. broad; the anterior margin (PI. VII. fig. 13) 
has a superficial furrow. 
The cavity of the body extends to about the region of the fourth papilla, it is fastened 
to the body-wall by septa of connective tissue, and by the renal tubes. 
The position of the intestines has been already described by me. 1 
The central nervous system has the cerebro-pleural ganglia very closely united to 
each other ; their two divisions but slightly distinguishable, the anterior is more 
flattened and slanting in front, the posterior division is thicker. The pedal ganglia are 
not much smaller than the cerebro-pleural, and are situated obliquely below them ; they 
are, however, not so thick ; from each ganglion are given off four stout nerves, bifurcated 
nearly from the root. The pedal commissure is barely one-third of the breadth of the 
ganglia themselves. In front of this commissure are the separated pleural and subcerebral 
commissures, and behind the pedal apparently a sympathetic. The buccal ganglia are 
rather large and rounded ; they are united by a commissure, which is at least one-third 
the diameter of the ganglia ; the gastro-oesophageal ganglia are about one-fourth the size 
of the buccal, and are provided with a short stalk. The nervus opticus is quite twice as 
long as the diameter of the central nervous system ; that portion of it nearest the eye 
shows black pigment ; the nervus olfactorius dilates into a small ganglion, nearly as big 
as the buccal ganglion at the base of the club of the rhinophore. 
The eyes are large, the lens 2 yellow in colour, the pigment black. I did not succeed 
in discovering the otocyst. There were no spicules in the leaves of the rhinophoria, nor 
in the skin ; in the latter there were, on the contrary, masses of variously sized unicellular 
1 Bergh, loc. cit., p. 292. 
2 The lens appeared in both eyes to be composed of a number of spherical pyramids; but this may have been a post- 
mortem appearance. 
