162 LIVERPOOL BIOLOGICAL SOCIETY. 
that it was present on the rocks at Hilbre Island in oreat 
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 
elands are placed just where an offensive organ would be 
most useful, and where the stinging cells are found in 
Folis, and it seems probable that their secretion has an 
acrid or some other objectionable property. 
The protective colouring of Doris bilamellata+ may be 
accounted for in one or both of two ways:—(a.) 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 (>) it may save the 
animal from being tried by fishes, &c., not sufficiently 
aware of its (to them) distasteful nature. 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. olis is a most 
distasteful form and has conspicuous colours of a warning 
* See this Report, p. 135 and PI. vii. fig. 9, gl’. 
+ See this Report, p. 133. 
~ A very similar case seems to be that of the two British species of Hermea 
as described by Garstang (loc. cit., p. 191). H. bifida has its conspicuous 
hepatic ramifications exceedingly like the branches of the red seaweeds of the 
genus Grtfithsia amongst which the animal lives. 4H. dendritica is coloured 
bright green so as to resemble Codium tormentvsum on which it lives. Both 
species are protectively coloured and have no stinging cells like those of Eolis, 
but they seem to possess the power of emitting, when irritated, an offensive 
fluid. 
ae eo 
