47 
in Pliny's days and for long afterwards ; then it disappeared ; 
within the last few years it has reappeared, fresh shoots out of 
an old trunk cut down (’which does not seem when standing to 
have been evergreen), again showing the old characteristic. 
This variety, we are told, could not be propagated elsewhere, 
the seedlings withering everywhere but in their native spot, no 
doubt from lack of some peculiarity in the soil or situation. 
We can, however, readily believe that, had the appropriate 
soil and situation been plentiful, this variety might have turned 
out its progenitor, have become confirmed in its difference, and 
been ranked as a remarkably distinct species. 
But further, variation extends also to instincts and habits of 
life ; acquired instincts are hereditary quite as much as natural 
ones. The case of the pointer is an excellent instance, the 
instinct of pointing being one known sometimes to occur as a 
variation, and being also one certainly transmissible by inherit- 
ance. It is highly probable that it was indeed originally 
nothing but an individual variation, become now by selection 
and inheritance the permanent characteristic of a race. Varia- 
tions of habits in domestic animals, such as different degrees 
of docility, preference for particular kinds of food, fondness 
for various pursuits, &c., are too familiar to every one to need 
especially insisting on. Nor is there any doubt that such 
variations are to some extent hereditary. To take but a single 
instance, this time from creatures in a state of nature: — the dread 
of man, undoubtedly hereditary in many wild species, is shown, 
by the experience obtained in newly-peopled islands, to be an 
acquired, not an original instinct. 
In the same way as instincts and habits may thus be occa- 
sioned by change of circumstances, as well as by natural vari- 
ability, so may differences in structure and development be 
brought about by altered conditions of life. Every one knows 
how largely use and disuse tend to modify powers ; few, how- 
ever, probably realize the extent to which this involves also 
modification of structure. The superior use of the right hand 
and arm in man renders it the strongest and most adaptive; it 
also lengthens and enlarges the bones composing them. Con- 
tinual practice in running will conduce to greater fleetness, 
which again depends in part upon the relative size of certain 
bones. Not only are persons born with short sight and long 
sight, but these can also be acquired by use. The sailor, 
habitually accustomed to descry distant objects, lengthens his 
sight, can see farther than others. The student, used to poring 
over his book, shortens his sight, can see nearer than others, 
but at the same time loses his power of seeing far off. Now 
what does this involve ? There is in the eye a wonderful power 
