438 M. Sars on the Distribution of Animal Life 



were individuals of species which, in shoal water, are brightly 

 banded or striped, that between 60 and 80 fathoms stripes and 

 bands seldom appear on our shells, esjDecially in the northern 

 provinces, but that from 50 fathoms and upwards colours and 

 patterns are well marked. 



Against the general tenor of these statements of Forbes, 

 that colours in individuals of the same species gradually dis- 

 appear according to the depth, Jeffreys has rightly declared 

 himself (British Conchology, vol. i. Introd. p. 49), and has 

 used his experience of mollusks to illustrate his meaning, 

 which I can also confirm by numerous examples. 



Thus, to name some among many, and among other classes 

 than mollusks, the dorsal surface of Ophioscolex purpurea, 

 from 300 fathoms, is of as lively a bright red, or sometimes 

 dark red, as are individuals from 45-50 fathoms. Arctiaster 

 tenuispinus from 300 fathoms is as bright orange-red as from 

 30-50 fathoms. Ophiura abyssicola from 300 fathoms is of 

 the same light grey, sometimes pale rose-colour, with reddish, 

 chestnut, and dark-brown spots, as from 50-100 fathoms. 

 Onupkis quadricuspis from 300 fathoms has as bright an 

 opalescent gleam with two blood-red lines along the middle of 

 its back as individuals taken from 50 fathoms. The shell of 

 Pecten septemradiatus from 300 fathoms is as red and white- 

 speckled as from 20-30 fathoms. Astarte sulcata from 300 

 fathoms has a chestnut-brown epidermis the same as if from 

 5-10 fathoms. Natica Montagui from 250 fathoms appears of 

 a red-brown with a white band on its sutures, just as if from 

 15-20 fathoms. Eulima bilineata from 300 fathoms is found 

 with two yellow spiral bands as bright as from 15-20 fathoms; 

 and many more. 



Sometimes, indeed, it happens that lively colours seem in 

 some degree to fade with the depth, as e. g. Hippolyte polaris, 

 which in the laminarian zone has many large blood-red and 

 two sky-blue spots on the hinder part of each segment, at 

 200-250 fathoms is paler, the red disappearing, and has 

 scarcely any sky-blue spots. 



Thus Forbes's assertion is certainly not universally true. 

 It seems to have been made under the influence of an idea, 

 held by many naturalists, that light could not penetrate deep 

 into the sea, and that therefore in the greater depths of the 

 sea complete darkness reigned, in which all colours must dis- 

 appear, as in those creatines (e. g. Proteus, Amblyopsis, &c.) 

 which inhabit subterranean caves ; and he was doubtless con- 

 firmed in his opinion by finding, as he occasionally did, at 

 depths under 100 fathoms, white or colourless individuals of 

 species elsewhere coloured. But such albino varieties occur 

 at all depths. 



