162 LIVEEPOOL BIOLOGICAL SOCIETY. 



that it was present on the rocks at Hilbre Island in great 

 abundance, in very prominent and exposed situations, 

 and that its colouring was not protective but rendered 

 it conspicuous. Our experiments at the Aquarium next 

 showed us that this nudibranch is distasteful to fishes and 

 other shore animals, but for a time we did not understand 

 why. Lately, however, we have found that besides the 

 abundant mucous glands scattered over the integument, 

 Ancula possesses special large glands,* occupying the 

 apices of the cerata and opening on the exterior. These 

 glands are placed just where an offensive organ would be 

 most useful, and where the stinginoj cells are found in 

 Eolis, and it seems probable that their secretion has an 

 acrid or some other objectionable property. 



The protective colouring of Doris hilamellata\ may be 

 accounted for in one or both of two ways:— (<2.) It may 

 serve to protect from certain other shore animals which 

 we have not yet tried, and to which the spicules and mucus 

 of the Doris are not objectionable, and {h) it may save the 

 animal from being tried by fishes, &c., not sufficiently 

 aware of its (to them) distasteful nature. t It is obvious 

 that if an animal is not thoroughly objectionable, and has 

 not yet become conspicuous with warning colours, it will 

 be better for it to be protectively coloured. Eolis is a most 

 distasteful form and has conspicuous colours of a warning 



* See this Report, p. 135 and PI. vii. fig. 9, gl'. 



t See this Report, p. 133. 



X A very similar case seems to be that of the two British species of Hermcea 

 as described by Garstang (loc. cit., ]). 191). H. bifida has its conspicuous 

 hepatic ramifications exceedingly like the branches of the red seaweeds of the 

 genus Oriffithsia amongst which the animal lives. Ff. dendritica is coloured 

 bright green so as to resemble Codium tormentosum on which it lives. Both 

 species are protectively coloured and have no stinging cells like those of Eolis, 

 but they seem to possess the i)ower of emitting, when irritated, an ofi'ensive 

 fluid. 



