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Textes en anglaisLyell, Charles, Principles of Geology (extract of Vol. 2) • CHAPTER III.
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WE endeavoured in the last chapter to show, that a belief in the reality of 
species is not inconsistent with the idea of a considerable degree of 
variability in the specific character. This opinion, indeed, is little more than 
an extension of the idea which we must entertain of the identity of an 
individual, throughout the changes which it is capable of undergoing.

If a quadruped, inhabiting a cold northern latitude, and covered with a warm 
coat of hair or wool, be transported to a southern climate, it will often, in 
the course of a few years, shed a considerable portion of its coat, which it 
gradually recovers on being again restored to its native country. Even there the 
same changes are, perhaps, superinduced to a certain extent by the returns of 
winter and summer. We know that the Alpine hare * and the ermine † become 
white during winter, and again obtain their full colour during the warmer season 
; that the plumage of the ptarmigan undergoes a like metamorphosis in colour and 
quantity, and that the change is equally temporary. We are aware that, if we 
reclaim some wild animal, and modify its habits and instincts by domestication, 
it may, if it escapes, become in a few years nearly as wild and untractable as 
ever ; and if the same individual be again retaken, it may be reduced to its 
former tame state. A plant is placed in a prepared soil in order that the petals 
of its flowers may multiply, and their colour be heightened or changed ; if we 

* Lepus variabilis. - Pallas.

† Mustela erminea. - Linn.
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Auteur et directeur de publication : Pietro CORSI,
Hébergement : Centre de Calcul de l'IN2P3-CNRS.