NUDIBKANCHIATA 01^' THE L.M.B.C. DISTRICT. 147 



Part II. Epipodial Natuee of the Cerata. 



In a paper* laid by one of us before the British Associa- 

 tion last September, it was suggested that all the various 

 projections from the sides and back of Nudibranchs known 

 as cerata are to be regarded as epipodial papillae, or out- 

 growths from a more or less distinct epipodial ridge. 

 And Garstang f has independently arrived at the same 

 conclusion in his recent Report upon the Nudibranchs of 

 Plymouth Sound. 



Pelseneer has lately drawn attention I to the presence 

 and condition of the epipodia in Trochus and other Rhipi- 

 doglossate Gastropods, but he does not consider these 

 structures as being homologous with the large epipodial 

 flaps of Aplysia and other Opisthobranchs and Pteropods. 

 For these latter he uses the term parapodia, introduced 

 by von Jhering, and open to the objection that it is already 

 appropriated by a totally different structure in another 

 group of animals. But the condition of the parts in 

 Trochus is so very similar to that found in Poli/cera and 

 Idalia, and the dorso-lateral processes of the two latter 

 forms are so clearly comparable with the large lateral flaps 

 of Aplysia, that we are inclined to regard all these projec- 

 tions as being homologous structures, entitled to be con- 

 sidered as epipodial in their nature. 



We now give figures of a series of transverse sections 

 (PL VI.) for the purpose of showing the condition of the 

 epipodial structures in a number of different forms of 

 Nudibranchs. 



The typical epipodia are seen in Ehjsia (PI. VI. fig. 1) 



* Herdman on the Struct, and Functions of the Cerata, &c., Brit. Assoc. 

 Report, 1889 (abstract only), and j)ublished in full in Quart. Journ. Microsc. 

 Science, vol. xxxi., p. 41. 



t Journ. Mar. Biol. Assoc, vol. i. no. 2., p. 181. 



X Sur r 6pipodium des Mollusques, Bull.^Sci., 1888, p. 182. 



