46 
Address of the President at the Annual Meeting, 
are altogether valueless for such a purpose. Thus the family 
of Felines, taken as a whole, is one in which great importance 
may be attached to the markings of the surface ; so that, 
although the skeletons and teeth of the various species differ 
but little from each other except in size, yet the constancy of 
these surface-markings in large sets of individuals, suffices to 
mark each set as specifically isolated from every other. We 
find, moreover, that the Felines generally are but little capable 
of adapting themselves to a variety of external conditions, so 
that each species is limited to a certain geographical area, 
beyond which it has no tendency to disperse itself, and within 
which it has no disposition to vary. But when we turn to 
the domestic Cat, we find a completely opposite state of things ; 
for we at once perceive that this species is endowed with a 
most e^tx^oxdindiYy capacity for variation ; in virtue of which 
we not only find its constitution adapting itself to a great 
diversity of climates, of food, of habits, <&c. ; but all those 
nameless influences which may be included under the general 
term ' domestication,' tend to produce a special tendency to 
want of uniformity in that very particular — the surface-mark- 
ing — which is so constant in the undomesticable species. 
Thus, then, we see that the capacity for variation, which 
seems inherent in the constitution of certain beings to the 
exclusion of others, not only enables the former to extend 
themselves where the latter cannot follow them, but brings 
them under a new set of influences, which themselves tend to 
increase the range of their variation. Asa general rule, there- 
fore, we may expect that a widely-diffused species should ex- 
hibit a considerable extent of this range ; which may show 
itself not merely in obvious adaptations to diversities of 
climate and of external circumstances, but also in departures 
from what we are accustomed to regard the typical character, 
of a kind that does not seem reducible to any known opera- 
tion of causes. 
Having for many years made this topic a special subject 
of inquiry, from its connexion with the much-discussed ques- 
tion of the specific unity or diversity of the human races, I am 
able to confirm the curious general principle long since laid 
down (though probably in too formal and stringent a manner) 
by Mr. Swainson, that in every natural group, whether large 
or small, there seem to be some divisions which are endowed 
with a remarkable degree of this capacity for variation, whilst 
there are others which are as remarkably deficient in it ; and 
hence, that characters which are quite sufficient for the sepa- 
ration of species in the latter case, must be regarded as merely 
indicative of individual variation in the former. 
