Coloration of Echinus angulosus, A. A<jass. 197 



the body at any point and give rise to temporary pigmenta- 

 tion. He regards the colouring-matters as either waste- 

 products or effete respiratory pigments which, when cast out 

 from the wandering cells or leucocytes, produce a coloration 

 of the skin. List holds that " protein crystalloids in the 

 nuclei of the wandering cells of Echinoids probably become 

 pigment granules." 



It may be interesting to compare Echinus angulosus with 

 an equally bright-coloured form of northern seas, namely 

 Slrongylocentrotus lividus, the long spines of which vary " in 

 colour from olive to violet purplish or even yellowish tint, 

 tipped with yellow and all intermediate shades." Camerano 

 showed that there are no constant differences in colour which 

 would differentiate sex, and Bordaa has pointed out that the 

 ovaries of this species are palatable. Now, according to 

 M'Intosh, the colours of Strongylocentrotus are not protective, 

 and, indeed, it would be difficult for one to regard the colours 

 as either " protective " or " warning," as this form, according 

 to Agassiz and Caillard, sometimes conceals itself by digging 

 out cavities in the solid rock, even in such as granite. 

 MacMunn has shown by means of the spectroscope the 

 presence of a respiratory pigment (" echinochrome ") in 

 Strongylocentrotus lividus, and this is probably also found in 

 the leucocytes, but it has not yet been clearly shown what 

 exact relation this pigment bears to the integumentary 

 coloration. 



In the opinion of the writer it is not necessary, even to a 

 firm believer in the principle of " Natural Selection," that 

 one should find in every case an adaptive explanation of the 

 colour of a species. It is not essential to hold that every 

 characteristic, colour or otherwise, which an animal possesses 

 is adaptive. 



The coloration of Echinus angulosus is not sexually 

 dimorphic, and it cannot be grouped under the headings 

 "protective" resemblance, "aggressive" coloration, "warn- 

 ing" indication, except by excessive exercise of imagi- 

 nation and ingenuity. The meaning of the coloration of 

 E. angulosus is to be sought for in the internal physiological 

 processes (probably respiratory or excretory) of the animals 

 themselves. The variable tegumentary colouring of E. angu- 

 losus is probably due to by-products or waste-products 

 produced during the metabolic processes. 



I append a list of the synonyms and distribution of Echinus 

 angulosus quoted from Agassiz : — 



Cidaris miliaria angulosa !, Klein, 1734, Xat. Disp. Ech. pi. iii. figs. A, B. 



