78 INTRODUCTION. 



It was this modification which in ancient times 

 so greatly excited admiration at the beauteous ver- 

 satile tints of the dying (misnamed) Dolphin of 

 the Mediterranean — the Cori/phcenahippurus; and 

 which in later days drew forth the remarks of 

 Mr. Borlasse, the learned author of the Natural 

 History of Cornwall. " The coloured streaks of 

 the Mackerel," he observes, " are justly admired 

 when the fish is dead; but they are greatly su- 

 perior in beauty when it is alive. When first 

 caught, its colours are strong and lively; the 

 streaks on the back are of a full dark-blue green, 

 the ground being willow-green; but as the fish 

 grows fainter, the streaks, losing their strength, 

 grow paler, and the blue goes off. Put the fish 

 again into a pail of sea- water, it will begin to move, 

 and as it revives, the colours renew their lustre ; 

 take it out of the water, and the colours faint and 

 fade away as before. However inexplicable, there- 

 fore, that configuration of parts may be, to which 

 the tints are attributable, it is plain, in this case, 

 that the height of the colouring is owing to the cir- 

 culation of the juices in those fine capillary vessels 

 and membranes of which the entire covering is 

 composed : as the blood stagnates, the mass settles 

 into a state of rest, incapable of reflecting the rays 

 of light with equal vivacity. (Lib. cit. 269.) Some- 

 thing, however, we may add, is probably owing in 

 this instance to the different degrees of the trans- 

 parency of the scales. 



But that a great and almost an immediate change 



