MARINE BIOLOGICAL STATION ON PUFFIN ISLAND. 15 



and noticed that they were swayed backwards and for- 

 wards in the water, but remained securely anchored by 

 their tails. 



Ancula is not protectively coloured ; and as it has 

 no cnidophorous sacs with stinging cells, like those of 

 Eolis, its bright white and yellow colouring and con- 

 spicuous appearance on dark rocks seems at first in- 

 explicable. From experiments made at the Aquarium 

 last spring I came to the conclusion that it is distasteful 

 to fishes, and possibly it is the secretion of certain large 

 compound glands at the apices of the cerata or dorsal 

 processes which is of an offensive nature. 



Doto coronata, when it is found at Hilbre Island, gene- 

 rally occurs on colonies of the Zoophyte Clava multicornis ; 

 but Dr. Sibley Hicks tells me that he has found it in our 

 district, on the sides of the body of the sea-anemone 

 Anthea cereus, lying in cavities which it had apparently 

 eaten out for itself. Another rare Nudibranch which we 

 found at Hilbre in March was Cratena viridis, of which only 

 two specimens had been found before in our district, one at 

 the Isle of Man and the other at Puffin Island. A fourth 

 was dredged later in the summer in Rhoscolyn Bay, Angle- 

 sea, during the cruise of the "Hyaena." 



Altogether we have now recorded forty-tln-ee species 

 of Nudibranchs in our district, of which thirty-one have 

 been found at Hilbre Island and seventeen at Puffin 

 Island. Besides affi^rding opportunities for investigations 

 into the condition of the stinging organs in various species 

 of Eolids, and into tlie relation of tlie colouring to the 

 environment in other forms of Nudibranclis, these speci- 

 mens have enabled us to make a comparison of the epi- 

 podial structures throughout a series of genera, from 

 which we have arrived at the conclusion that all the dorso- 

 lateral projections, or cerata, of Nudibranchs, often the 



