23t5 Prof. W. C. M'liitosli oh the 



they can dart upward very actively, nor will the explanation 

 altofrethcr puit the frog-fish (Lophi'us). Some of the finest 

 silverv bluish-green or yellowisli touciies of the short-spiued 

 Cottiis are under the throat. The gorgeous colours of several 

 of the liritish wrasses do not appear to be either for warning 

 or protection, nor do they appear to be connected with Sexual 

 Selection. Moreover, it may be asked if the white under 

 surface of many terrestrial mammals has been acquired for 

 the same reason, viz. rendering them invisible against the 

 sky when viewed from beneatli. In connexion with this 

 explanation it has also to be remembered that the enemies of 

 fishes do not always look at them from these points of view. 

 Again, freshwater and marine fishes agree in regard to tliia 

 coloration, and whilst the dark dorsal surface does aid in 

 rendering the fishes obscure, the constant movement of the 

 tail in streams makes them obvious enough. Besides certain 

 silvery fishes with laterally compressed bodies are very 

 conspicuous and tlie ventral edge is thin. Thus in the tidal 

 pools in May young sand-eels of 4 inches swim in parallel 

 ranks, conspicuous by their finely iridescent green backs and 

 silvery sides, or sport amongst the fringing seaweeds like 

 flashes of silvery light in the sunshine. Such forms are no 

 less conspicuous in the open sea — indeed, their only safety in 

 this respect is immersion in sand. The dull bluish-black 

 dorsum of the herring renders it less visible, but the approach 

 of an enemy causes it to dart aside and expose the flashing- 

 silvery body. 



Prof. Moseley gives the instance of Antennarius, which is 

 coloured, like the gulf- weed [Sargassum), with spots of white 

 to imitate the patches of Memhranipora. Bright s))ots of white 

 are common in young sea-scorpions, young lump-suckers, 

 and others, but it w^ould be difficult to draw a similar con- 

 clusion. The adult shanny and the gunnel are certainly 

 coloured in harmony with their surroundings, just as the 

 upper surface of many flat-fishes is. The same may be said 

 of other blennies. Mr. (larstang cites the black dorsal fin of 

 the weever as a warning colour, lest it should be mistaken 

 for the gurnard. The bold touches of black and other colours 

 on the dorsal fins of other fishes are not, however, thus to be 

 explained. 



Deep-sea fishes are black or white as if bleached (Moseley). 

 On the other hand, the pelagic young of the conger {Lepto- 

 cephalus) and of I'lagusia are transparent. 



The pelagic young of some fishes, e. g. the skulpin, have 

 the under surface darkly pigmented, yet its habits agree with 

 those of its fellows which have the same region translucent 



