304 Royal Society : — 



short, linear, pointed. Branchial plumes six (?), short, bi- 

 pinnated, of a purplish colour. Under parts deep vermilion- 

 red and speckled with darker red. Foot short, red. 

 Found near Sober Island, Trincomalee Harbour, 



Subgenus Onchidoris. 

 Ondddoris Leachii, Blainv. 

 Carncous, Body oval, about 1^ inch long. Mantle granular, 

 and studded with filamentous granules ; those on the posterior 

 third of the mantle often large, and appearing like small 

 branchial plumes. No dorsal tentacles. Two oral tentacles, 

 which appear to protrude through notches from under the 

 anterior edge of the mantle. The foot is broad, and occupies 

 nearly the whole of the under part of the mantle. The anus 

 opens on the under surface of the posterior part of the mantle. 

 Orifice of the organs of generation on the right side. 

 Found on rocks in the Inner Harbour. I have scarcely any 

 doubt that this is the Onchidoris described by Blainville from a 

 specimen seen in the British Museum, whose habitat was not 

 known. 



The colour of the animal is a light grey, mottled with black 

 spots in some specimens. In spirits, the filamentous granules 

 are not seen ; but when the animal is alive, they are distinctly 

 apparent, and the contractile character of the filaments is very 

 observable, especially in the larger ones. 



PROCEEDINGS OF LEARNED SOCIETIES. 



ROYAL SOCIETY. 



November 18, 1858.— Richard Owen, Esq., V.P., in the Chair. 



" Further Observations on the Power exercised by the Actiniae of 

 our Shores in kiUing their prey." By R. M'Donnell, M.D. In a 

 letter to W. Bowman, Esq., F.R.S. 



In the course of last winter I had the honour, through your kind- 

 ness, of making a communication to the Royal Society "On the Power 

 exercised by the Actiniae of our Shores in killing their prey ;" allow 

 me now, through the same medium, to correct the view which I 

 was at that time led to adopt, that this power is due to electrical 

 influence. 



In the communication alluded to, the idea of these creatures being 

 electrical was based on the fact, that when the nerve of a frog's 

 limb, prepared after the manner of Matteucci's galvanoscopic frog, 

 is seized by the tentacles of an Actinia, contractions of the muscles 

 promptly ensue. It was admitted, however, that all attempts to pro- 

 duce deflection of the galvanometer-needle had failed, and this being 



