Recherches sur les Poissons Fossiles. 



323 



markable phenomenon in fishes depending on the abundance 

 of pigments, their differences, and the rapidity with which 

 they are secreted and absorbed, is the changes of colour 

 which belongs to many species at different seasons of the 

 year. In the time of spawning, for example, or rather during 

 their time of growth, or when excited to violent movements, 

 or even after their death, when they have been exposed to 

 different atmospheric influences. 



All the species which I have observed, present at the 

 period of spawning, even more vivid and marked tints than 

 usual, the points of coloured pigment that are not ordinarily 

 seen towards the back, are then extended also on the flanks 

 and belly which they embellish. Even the (at other times) 

 uncoloured regions of the body are at this period also cover- 

 ed with various tints ; the abdomen, for example, is marbled, 

 and the insertions of the fins are red or orange, and the 

 belly partakes of various shades of these different colours. 

 During the development of fishes, we see also their skin and 

 their fins presenting the most fanciful and brilliant tints, 

 although at the period of their birth they are nearly all 

 white and transparent. In making drawings of living fish, 

 I have yet another curious observation to make on their 

 colouration : it is, that when they are irritated, or exerting 

 violent efforts to escape from their confinement, they pre- 

 sent the most animated, as well as the most rich and cha- 

 racteristic of their colours, they become pale, or even 

 completely lose their colours, which they again slowly re- 

 cover. I have not however observed this fact often in the 

 Zingel (Aspal Zingel), in the Trout of the rivers (Salmo 

 Fario), in the Lotte {Lota Fluviatilis,) and in the Silure 

 (Silurus Glanis.) To me it appears capable of explana- 

 tion by the supposition of an abundant secretion and sud- 

 den reabsorption of the coloured pigments. After death, 

 all the green parts of fishes very soon change to blue 

 on exposure to the air ; thus nearly all blues represented 



