REPORT OH THE NUDIBRANCHIATA. 
95 
cerebro-pleural ganglia are short, rather longer than broad ; the cerebral and the pleural 
ganglia are of nearly equal size ; the pedal ganglia, lying at the outside of the middle of 
the former, nearly as large as the pleural and roundish in outline. The large common 
commissure is nearly half as long again as the mean diameter of the central nervous 
system ; all the three commissures are contained in a common sheath. The proximal olfac- 
tory ganglia are rather small, nearly sessile ; the distal ones at the base of the club being 
only a little smaller than the proximal, and roundish. The buccal ganglia are shortly -pyri- 
form, plano-convex, the broad ends passing almost immediately one into the other ; the 
gastro-cesophageal ganglia are short-stalked, nearly one-eiglith the size of the preceding. 
The eyes are very short-stalked, the greatest diameter ‘3 mm., slightly flattened on 
the lower side, with pitch-black pigment and rather large pale-yellowish lens. The 
otocysts are visible as chalk -white points on the lower side of the central nervous system ; 
they are almost spherical (PI. I. fig. 19), nearly T2 in diameter, and closely packed with 
some hundreds of the usual otoconia, the largest of which were '009 mm. in diameter. 
The thin leaves of the rhinophores , furnished only here and there with isolated knots, 
were stiffened with long (up to about '8 mm.), fusiform, strongly hardened spicules of 
about '025 mm. in diameter. The spicules were still more numerous in the stalk and 
generally in the axis of the rhinophoria, where they had almost completely replaced the 
other tissue. The tentacles had a very large number of spicules lying in different direc- 
tions, but diminishing in number towards the point. There were only a small number 
at the head. The very low nodules of the back were richly furnished with (figs. 20, 21) the 
usual kind of spicules, the points of which often projected (PI. II. fig. 1) on the surface. 
A quantity of similar spicules, most of them very long, were present on the lower side of 
the mantle-border ; they were placed very irregularly, and often formed large heaps and 
node-like points. The relation of the spicules was exactly the same in the sides of the 
body and in the pedal sole. There were only a few larger hardened cells and spicules 
present in the interstitial connective tissue, even in the periphery of the principal 
efferent ducts of the reproductive apparatus. 
The mouth tube was large, nearly 6 '5 mm. long, and 7 mm. broad behind, somewhat 
flattened; the inside, for rather more than the posterior third, was of a bluish-black colour. 
The three pairs of retractors were very strong, with an additional weaker more mesially 
situated pair above ; the inside showed the usual upper circular fold and also the upper 
three-fourths of the longitudinal folds of the bluish-black colour shining through exter- 
nally ; longish spots of the same colour appeared thickly scattered below. — The bulbus 
pharyngeus was strong, nearly 6 '5 mm. long by 7 mm. broad and 5'5 mm. high ; the 
sheath of the radula still projecting backwards about 2 '2 mm.; the long retractors very 
strong. The labial disk was large, and covered with a white cuticle ; round about, and 
near the perpendicular- buccal fissure, this last passes into a chitinous yellow prehensile 
ring, which only enters the mouth a little way, and has a mean diameter of '8 mm. This 
