COLORATION AND MIMICRY 287 



marking, but with, the exception of those in the Cephalopoda 

 none clearly indicative of usefulness. 



The red, radiating lines of the "Sunset Shell " (Psammobia 

 vespertina) ; the brown, waved lives of Pectunculus ; the red, 

 or red and green, stripes of Trochus magus ; the red and blue 

 of Trochus zizyphinus, and a host of other shell-bearers, is 

 plainly neither sexual, inimical, warning, nor luring. 



It has been said that the Nudibranchi and Opisthobranchi 

 have colouring as protective coloration. Here again there 

 are great objections to be raised. These molluscs are not 

 good to eat. This I have remarked by very long experience 

 in the field, and it has been made a subject of scientific 

 test by Professor Herdman. In his experiments only once 

 or twice, out of a large number of trials, did a fish eat one. 

 And yet, with one exception (Aplysia), the colours are not 

 warning, but what could be termed mimical the reverse 

 of what we should expect. 



(I refer, of course, only to those of our shores ; the 

 gorgeous colours of the Nudibranchi of deep sea and of 

 foreign lands may be warning.) 



Aplysia punctata is strikingly conspicuous dark,- almost 

 black, purple with white dots and creeping on a sandy 

 bottom is very easy to see. This may be " warning," for 

 Aplysia is not good to eat, but it has a " warning " quite 

 independent of this : its powerful odour of cedar would 

 turn off any of its enemies, which would most likely be 

 ground feeders congers, rays, and dog-fishes and these 

 hunt chiefly by scent. 



Aplysia depilans is less conspicuous, grey or brown. (I 

 am inclined to think these two species are one, for I find 

 plenty of specimens not clearly referable to one species 

 more than the other.) 



Mr Beddard, as I have already said, lays stress on the 

 transfer, unaltered, of the coloured pigments of the food 

 to the feeder, thus accounting for the colour of the latter. 



