34 JOURNAL OF MARINE ZOOLOGY AND MICROSCOPY. 



of the family Leptoclinidae, of which on this coast I know a bright 

 sky-blue species, and others of lilac and of purple in varying shade. 

 Many fishes are striped (male of Labrus mixtus) or otherwise 

 ornamented with bright blue ; but only among the Teleostei, the 

 most specialized of fishes. There are certainly cartilaginous fishes 

 to which the term blue is affixed, such as the Blue Shark, but such 

 colour is rather grey or drab and can only be termed blue by a 

 stretch of courtesy. 



All this is strong evidence, but we can obtain further confirma- 

 tion by looking at the problem in a different light. Presuming 

 blue to be furthest from the primitive colour, such hued animals 

 must have passed through the scarlet stage at a later date than the 

 yellow, and we should expect the species and genera nearest related 

 to be of the scarlet hue rather than of the yellow. And it is so. The 

 nearest relations — and less specialized too — of the lobster on our 

 coasts, the Norway lobster (N&phrops norvegicus) and the two 

 craw-fishes Palinurus and Scyllarus are all scarlet, not yellow. The 

 star-fishes, more primitive echinoderm forms than the so frequently 

 purple coloured sea-urchins, seldom or never in our seas get beyond 

 yellow, orange, and scarlet. Regarding the Ascidians, the blue and 

 lilac Leptoclinidse have, as most closely related species, several of deep 

 scarlet and blood red, a few of orange, and but one or two of yellow 

 and of white. 



The converse holds true. Such animals as cling with intensity 

 to the primitive white, show in their nearest coloured relatives the 

 light end of the scale, yellow and orange, rather than purple and blue 

 or even scarlet. The sponge phylum being more homogeneous and 

 showing less specialization than any other serves admirably as a test, 

 and as already mentioned the only calcareous sponge I know to 

 be ever coloured in our waters, viz., Ascetta coriacea, is normally 

 white, occasionally canary yellow, and only rarely orange. The 

 Plumose anemone (A. dianthus) normally white, has a pale orange 

 variety, and again, the snowy Alcyonium digitatum is also occa- 

 sionally orange. 



To summarise these conclusions : — 



I. White is the prevailing colour of the least specialized animals 



in the most primitive phylum of the Metazoa — viz. : the 



calcareous sponges. 



II. Yellow and orange follow closely and are the characteristic colours 



of those coloured animals most closely related to white ones. 



III. Blue and purple are characteristic of the most specialized 



among the most highly developed phyla — e.g. the sea- 

 urchins among the Echinoderms, the lobster among decapod 

 Crustaceans, and the crusting compound Ascidians. 



IV. Animals most closely related to blue and purple species, are 



mostly scarlet, red, or deep orange in hue. 



