OF VARIETIES. 
85 
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, passes 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. 
OF 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 difference of tint, &c., from the typical species inhabiting 
the same places ; but the greatest part of the varieties are 
purely accidental, and offer 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- 
