On the present state of Zoology. 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.f 
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. 
