Colurittion of Marine Aniinah. 231 



and the enormous powers of reproduction, suffice in some 

 cases tor satety. Tliose wliich perforate rocks, wood, and 

 other media are, as a rule, white, yet the dale-shell {Litho- 

 domvs) has dark brown valves, whilst Modiolaria in the tests 

 of Ascidians and in sponges is feebly tinted. The species 

 which buirow in sand have di\erse and often bright tints, 

 such as l*s<ivimoh{a and Tellina^ dull brown, as in Cyprina, 

 or pale, like the cockle and Thracia. Littoral forms are 

 likewise varied. 'J"he mussel is dark blue or purplish blue on 

 mud or rock ; Galeomma with its outspread valves on the 

 under surfaces of stones is pure wdiite. Area in the chinks of 

 rocks is dull grey, and Lima hiatis has brilliant orange fringes, 

 but the animal makes a nest. 'JMie beds of sedentary dull 

 greyish oysters and the brownish-black horse-mussels in the 

 adjoining area under water are in contrast with the more 

 brightly tinted and free scallops in similar regions. 



There ia endless variety under the same circumstances, 

 but no ceitainty as to protective or warning coloration or 

 sexual changes in the valves of marine forms. 



It is interesting that pelagic young mussels and the slightly 

 older forms which settle on zoophytes in myriads are differ- 

 ently tinted from the adults. The latter (young mussels) 

 especially harmonize with their surroundings. The pelagic 

 young of marine lamellibranehs (after the formation of the 

 shell>), indeed, seem to approach each other more or less 

 closely. 



The parasitic bivalves, like Montacuta siihstriata on Spatan- 

 gus purpureuSj are in harmony with their surroundings, 

 though as regards coloration they are pale and more or less 

 trans])arent. 



Coloration in the univalves (Gastropoda) has no apparent 

 relation to their acceptability to forms which prey on them, 

 and therefore has no protective or warning functions. All 

 the available smaller lorms — whatever their colour may be — 

 are equally palatable to the haddock, which, as Edward 

 Forbes said, is a great conchologist. In their pelagic stages, 

 it is true, they are less brightly tinted, and thus may be held 

 to be protectively coloured ; but other young forms, which 

 are not pelagic, are of similar pale or neutral hues, so that 

 there is room tor doubt. The question may well be asked. 

 Are the bold bluish iridescent streaks of Jlelcion pellucidum 

 equally protective or warning in the young on the dark blades 

 ot the tangles in the rock-pools, and on the adults hidden 

 under the hard roots of the same seaweed ? 



Protective coloration iti the Gastropods is exhibited by 

 Ovula patu/a on (Jorgonia verrucosa (Poulton) and Ovulum 



