INNERVATION OF CERATA OF SOME NUDIBRANCHIATA. 593 
in former papers.!. The relations of the buccal mass, odonto- 
phore, and cesophagus to the nervous system, and the constitu- 
tion of the body-wall are alsoshown. Figs. 29 to 31 show the 
histology of the ganglia. The largest nerve-cells, as in other 
forms, are here on the surface. Fig. 830 shows the posterior 
surface slice of the right cerebral ganglion from the next section 
to that drawn in fig. 29. It is entirely composed of large poly- 
gonal cells with huge reticulated nuclei, each of which has a 
single very distinct nucleolus, which, again, sometimes has a 
distinct central spot (as in the cell marked x. e. in fig. 30). 
Fig. 29 shows on the left side at the top the next section of that 
cerebral ganglion, passing forwards, and it is also nearly all large 
cells; while the pedal ganglia below in the same figure, and 
also in fig. 81, show that the central parts of the ganglia are 
composed of small rounded or fusiform cells and interlacing deli- 
cate nerve-fibres. These fibres and the small cells come to the 
surface where a commissure or a nerve leaves the ganglion (see 
pedals of fig. 31). 
CoNncLUSION. 
We have shown, then, by the examination of this series of 
types, that instead of the cerata of Nudibranchs being always 
innervated by the pleural ganglia, as Pelseneer supposes,” or 
always supplied by pedal nerves, as we had expected to find 
when we commenced the investigation, there are, in fact, 
various arrangements of the nerve-supply. The dorso-lateral 
processes of the body-wall which we call cerata may be sup- 
plied entirely by the pleural ganglia (e. g. Polycera and 
Ancula), or chiefly by the pleural with a small supply from 
the pedal by means of a pleuro-pedal anastomosis (De ndro- 
notus), or entirely by the pedal ganglia (Tergipes), or chiefly 
by the pedal ganglia with a small independent accessory supply 
from the pleural (as in Facelina). 
If, then, we take the nerve-supply as a sure indication of 
1 ©Quart. Journ. Micr. Sci.,’ vol. xxxi, p. 41; and ‘Trans. Liverpool 
Biological Society,’ vol. iv, p. 181. 
2 * Bulletin Scientif.,’ t. xxiii, p. 439, Aug. 18th, 1891. 
VOL. XXXIII, PART IV.—NEW SER. Ee 
