90 
THE VOYAGE OF H.M.S. CHALLENGER. 
covered with nodules (PL I. fig. 15) of various sizes, up to - 5 mm. in diameter; the largest, 
fewer in number, short, cylindrical or rather hemispherical, and occasionally slightly 
constricted at the base. Similar nodules, partly large, partly smaller, are found on the 
margin of the simple round rhinophore-openings ; likewise on the simple margin of the 
branchial slit, where they sometimes alternate in size (fig. 14). The club of the rhino- 
phorict is strong, with nearly twenty-five broad, thin leaves. The branchia is composed of 
from eleven to twelve slender leaves, simple below, bipinnate and tripinnate above. The 
anal papilla is low, obliquely truncated ; beside it, to the right, is the renal pore. 
The (external) oral orifice is strongly contracted; the tentacles, short, fold-shaped. 
The foot strong ; the anterior margin with deep furrow and rounded corners, the tail 
somewhat pointed. 
The intestines are not visible through the body-wall at any point ; the peritoneum is 
colourless. 
The central nervous system (PL I. fig. 13) is not much flattened. The cerebro -pleural 
ganglia (fig. 13, ab) kidney-shaped, the two divisions almost equal in size; the pedal ganglia 
(fig. 13, c,c) roundish in outline; the large common commissure (fig. 13, d) distinctly show- 
ing at the roots that it is composed of three separate commissures. The proximal 
olfactory ganglia (fig. 13, e,e) are developed on one side of the nerve ; the distal ones (fig. 
1 3 ,f) rather smaller and roundish. The optic ganglia (fig. 13) are roundish, sessile, rather 
smaller than the olfactory ones (fig. 13). The buccal ganglia at least four times as 
large as the proximal olfactory, roundish in outline, and connected by a very short 
commissure (fig. 13, g). The rather short-stalked gastro-oesophageal ganglia (fig. 13 ,h,h) 
are developed on one side of the nerve ; a little larger than the lower olfactory ganglia ; 
the nervus cesophagealis major is bifurcated, showing on the branches small ganglia. A 
short-stalked ganglion genitale (fig. 13, i) is connected with the right pleural ganglion. 
The short-stalked eye (fig. 13) has black pigment and an obscure chitinous yellow lens. 
The otocysts, visible under the magnifying glass as chalk-white points, are rather 
smaller than the eyes, spherical, filled with about sixty of the usual otoconia, of up to 
•02 mm. in diameter. The thin leaves of the rhinophoria are without spicules. The 
tough skin and the dorsal tubercles (fig. 15) generally have only a few larger, crumpled, 
hardened spicules, and smaller groups of hardened cells. Only a few hardened cells in 
the interstitial connective tissue. 
The mouth tube was large, nearly 3 mm. long, and the same in diameter ; the three 
pairs of retractors and the inside as usual. The bulbus pharyngeus rather larger than 
the mouth tube, 3’5 mm. long by 275 mm. high and 2 - 5 mm. broad; the thick sheath 
of the radula still projecting 1*5 mm. behind; the retractors as usual; the labial disk 
covered with a strong, faintly yellow cuticle, with a narrow (slightly radiate) oral fissure. 
The glittering chitinous-yellow radula of the strong tongue with ten rows of teeth plates, and 
with traces of two former rows at the point ; there were also in the radula-sheath thirteen 
