38 ANIMAL COLORATION. 



farther back. It can be hardly disputed that, were pigment 

 simply distributed by means of natural selection, sufficient 

 time has elapsed for the effects of this action to have ceased 

 or been reversed. And yet the coloration of the deep-sea 

 animals is, on the whole, similar to that of their shallow-water 

 allies. If natural selection has been the cause in the one 

 case, it ought to be in the other ; but there are serious reasons 

 for disbelieving in the share taken by natural selection (that 

 is, of course, in relation to environment, etc.) in affecting the 

 coloration of deep-sea animals ; the question, therefore, is 

 pressing: need natural selection be responsible for the colora- 

 tion of the shallow-water forms ? 



" Protective resemblances " are shown among deep-sea forms, 

 just as they are in the shallow water 1 . 



Professor Agassiz remarks upon "the many species of 

 Ophiurans attached to variously coloured Gorgouians, branching- 

 corals, and stems of Peutacrinus, scarcely to be distin- 

 guished from the part to which they cling, so completely 

 has their pattern of coloration become identified with it. 

 There is a similar agreement in coloration in annelids when 

 commensal upon starfish, mollusca, actinia or sponges, and 

 with Crustacea and actinia parasitic upon corals, gorgonians or 

 mollusks." 



In my own opinion these cases of resemblance are to be 

 explained by the parasite actually assimilating and depositing 

 in its own skin the pigments of its host ; but they are entirely 

 parallel to instances of protective resemblance among the 

 littoral creatures. 



Since the conditions of life in the dee}) sea are so different 

 from those of shallower coast water, we might expect, bearing 

 in mind the primary meaning of pigment (see p. 5), to see some 

 differences in the colour. 



