On the present state of Zooloyy. 25 



exhibit, while it lasts, the permanent character of a distinct climate, 

 in which may occur the same species of bird with its plumage, con- 

 sequently, from the action of that climate, permanently modified. We 

 regret that, in relation to this subject, we have it not in our power 

 to consult a memoir which is said to have been presented nearly two 

 years since, by M. Gloger to the Berlin Academy, treating expressly 

 on the modifications induced by climate on birds. We may, however, 

 quote a remark by M. Jacquemin, which leads us to think that the 

 above idea is far from problematical. He says, in allusion to M, 

 Gloger's memoir, that its author " has demonstrated in such a man- 

 ner as to leave no doubt, that individuals of one and the same species 

 of bird present different arrangements of colouring according to the 

 climates which they inhabit, and that one and the same individual, 

 amongst the birds of passage, changes during nearly the whole year 

 the colours of its plumage, according to the different climates through 

 which it passes."* If this be true, the question is, indeed, nearly at 

 rest. Or it is reduced simply to an inquiry into the amount of influ- 

 ence produced by such a cause ; and till some endeavour has been 

 made to assign the limits, the fact itself may well make us sceptical 

 respecting many of the species found in distant latitudes, which, al- 

 though presenting the closest affinity to some in Europe, have been' 

 considered as distinct by naturalists.^ 



We have dwelt so long on the above subject, that we can hardly 

 pursue the question first adverted to, as regards the limits of species, 

 through any of the other classes. In some of these, we may observe 

 variations not of colour only, to which, in the case of birds, such va- 

 riations are generally restricted, but, to a less extent, of form and 

 sculpture also, which may be due to causes of which as yet we un- 

 derstand little or nothing. Generally speaking, differences of this 

 nature are more to be depended upon than those of mere colour ; but 

 even these cannot always be trusted as indicating a distinct species, 

 until after examination of a large number of individuals. We shall 

 then see how far such variations retain their constancy ; and whether 

 there may not be found specimens of an intermediate character serv- 



* Ann. des Sci. Nat. 1834, torn. ii. p. 279. 



•f- These allied species have been considered different, principally on the ground 

 of their inhabiting such different geographical positions. But there is reason to 

 believe that too great importance has been attached to this circumstance, and 

 that the power of acclimation possessed by many birds is more considerable than 

 naturalists are inclined to suppose — See a few remarks on this subject, accom- 

 panied by a list of Birds common to various parts of the world, by Lieut. -Col. 

 Sykes. Notices of Commun. to the Brit. Assoc. 1835, p. 69. 



