OF VARIETIES. S5 



others. The green colour tarnishes after death, loses its 

 vividness, and passes to blue : it gives out its tint to alcohol, 

 which thus becomes coloured. The white almost always 

 loses its purity, and becomes faded or yellow, while the 

 bright yellow passes to white. It is the same with the 

 beautiful red tints, with which the bodies of many snakes 

 are adorned ; this colour almost totally disappears after 

 death, jDasses to a yellowish white or to a brownish hue. 

 The blue, so rare among the order of Ophidians, is in most 

 of them effaced, and the same happens to the spots of bright 

 green. Almost all the other intermediate tints tarnish, or 

 lose, at least in part, their brilliancy, after being exposed 

 to the action of alcohol, 



or VARIETIES. 



Among the varieties which are so often observed in the 

 reptiles of which we treat, we must regard many as due to 

 the influence of climate : others, generally very constant, 

 are only separated by discrepancies extremely slight, such 

 as diiference of tint, &c., from the typical species inhabiting 

 the same places ; but the greatest part of the varieties are 

 purely accidental, and oifer modifications as innumerable 

 as diversified. Every part of the animal is subject to these 

 accidental variations ; they principally consist in different 

 shades and distributions of the colours, in the form of the 

 scales of the head, in the length of the tail, in the number 

 of abdominal plates, sometimes it is the forms which are 

 subject to modification. Experience, and the constant en- 

 deavour to reduce as much as possible analogous individuals 

 to the architype, are the only means of smoothing the dif- 

 ficulties which beset the zoologist in the determination of 

 species. Setting out with these views, we must not regard 

 as species the varieties produced by climate, whatever be 

 their characters, even when they remain constantly the same 

 in the same place. The study of these local variations, 

 hitherto neglected, is of the utmost importance for an accu- 

 rate knowledge of the creatures which inhabit our globe. 

 We have, in consequence, taken care to introduce in the de- 



