Coloration of Echinus angulosus, A. Agass. 195 



appear black ; but this does not hold true for the other 

 varieties of colour, the blue and green &c. The various 

 colours of Echinus angulosus as seen in the rock-pools are 

 very conspicuous and show no similarity to their surroundings. 

 In a number of cases the tests of the species are sometimes 

 hidden by empty shells, stones, &c, and these, as held by 

 Sim roth for Toxopneustes lividus, may be a source of protec- 

 tion against the force of the waves on an exposed beach, and 

 also assist in collecting organic particles. 



The application of the theory of " warning" coloration to 

 the case of Echinus angulosus is also well-nigh untenable. 

 There is so much variety of colour in a group of this species 

 that one could not say that any definite colour was a 

 " warning " colour. It is true that the species is a more or 

 less gregarious one, and that a preying fish might easily 

 locate the colony ; but the greys to some extent neutralize 

 the blues, &c, and the effect of a colony all members of 

 which were one definite colour would, from this point of 

 view, be more efficacious as a "warning" mark. I have 

 already pointed out that the gonads of this species are used 

 as food by man, and I noted that the species occasionally 

 fall as prey to fishes with sufficiently powerful jaws, such as 

 the white stumpnose, the panga, and the daggerad. Agassiz 

 has also pointed out that the two more common species of 

 sea-urchins of New England are greatly eaten by the cod 

 and the haddock. M'Intosh has shown that the green-pea 

 urchin is frequently eaten by the haddock. It is of interest 

 that the brightly coloured Strongylocentrotus hvidus (in its 

 colour somewhat similar to the purple or blue forms of 

 E. angulosus) is eaten by cod and haddock, as pointed out by 

 Nordgaard. Semon has also shown that Echinoderma 

 sometimes serve as food for mollusca, which dissolve the 

 calcium salts by the secretion of sulphuric acid. Saville 

 Kent has directed attention to the fact that Echini are food 

 for Cestracion. Fourtau has shown that they may be eaten 

 by crabs ; Herdman, Johnstone, and Scott have alluded to 

 Echinoids in the stomachs of flat-fish. Apart from these 

 facts, the Echinoids must have their great mortality period 

 during their larval stages; for example, it has been pointed 

 out by Gardiner that the ova and larva? of Echinoderms are 

 food for corals, such as Euphjjllia. The adult forms are 

 well protected from enemies by their long spines, their 

 poisonous pedicellaripe, and their disagreeable smell. 



It is also impossible to hold that the colours of E. angu- 

 losus are cases of " aggressive" resemblance. The food of 

 Echinoids, as pointed out by Allen, mainly consists of fine 



