226 TEANSACTIONS LIVEEPOOL BIOLOGICAL SOCIETY. 



It has been suggested that our Hilbre Island specimens 

 are of a variety differing in the structure of the cerata from 

 the specimens examined by others. I have endeavoured 

 to obtain specimens of Dendronotus from other localities 

 but without success. For myself, I do not think it likely. 

 However, I shall be very happy to exchange some of our 

 Hilbre Island specimens for some of these supposed 

 " ceratal hepatic caecal " bearing forms, if by so doing 

 Drs. Bergh and Pelseneer can be convinced of the correct- 

 ness of my conclusions, at least with regard to the Hilbre 

 Island Dendronotus. 



II. The Inneevation of the Ceeata. 



In the Quarterly Journal of Microscopical Science, a 

 joint paper* was published by Prof. Herdman and myself, 

 in which we showed from the examination of a series of 

 types of Nudibranchs, that instead of the cerata being 

 always innervated by the pleural ganglia, as Pelseneer 

 had previously supposed,! or always supplied by pedal 

 nerves, there are in fact various arrangements of the 

 nerve supply. We found from our investigations that 

 " the dorsal lateral processes of the body wall, which we 

 call cerata, may be supplied 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 {Dendronotus), 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 the cerata are to be 

 regarded as homologous structures throughout the series 

 of nudibranchiata, the nerve supply cannot be taken as a 



* "On the Innervation of the Cerata of some Nudibranchiata," Vol. 

 XXXIV., p. 541. 



f" Bulletin Scient." t. XXIIL, p. 439, Aug. 18th, 1891. 



