432 Scientific Intelligence. 
has to maintain against the surrounding agencies that are ever tending 
to dissolve the vital bond and subjugate the living matter to the ordinary 
chemical and physical forces. Any changes, therefore, in such external 
agencies as a speciés may have been a adapted to exist in, will 
militate against that existence in a degree proportionate, perhaps in a 
geometrical ratio, to the bulk of the s aoc If a dry season be gradu- 
ally prolonged, the large mammal will suffer from the drought sooner 
than the small one: if such alteration of swe affect the quantity of 
vegetable food, the bulky herbivore will first feel the effects of st 
nourishment; if new enemies are introduced, the large and conspicuous 
quadruped or bird will falla prey, while the smaller species conceal them- 
selves and escape. Smaller animals are usually also more prolific than 
larger ones. “The eee presence, therefore, of small species of a 
mals in countries where larger species of the same natural families 
formerly existed, is not the —e . any gradual diminution of the 
size of such species, but is the resu circumstances which may be 
illustrated by the fable of the ‘ Oak. aa the Reed;’ the smaller and 
feebler animals have bent and accommodated themselves to to changes 
which have destroyed the larger species.” No doubt the type-form of 
any species is that which is best adapted to the conditions under which 
such species at the time exists; and as long as those conditions remain 
unchanged, so long will the type remain } as varieties departing there- 
from being in the same ratio less adapted to the environing conditions of 
existence. But, if those conditions change, then the variety of the spe- 
cies ve an antecedent date and state of things will become the oe 
according to the principle of a succession of varieties in time. : 
tion of fossil remains is also still needed to make known the asto-type 
in which varieties, analogous to the observed ones in existing —— 
might have occurred, so as to give rise ultimately to such extreme forms 
as the Giraffe, for example. 
Man.—The aboriginal laws of the geographical distribution of plants 
and animals, have been modified from of old by geological and the con- 
comitant climatal changes; and much more by man since his introduction 
upon the globe. The ter plants and animals which he has carried 
—the dog—is 
lied . a few well-marked i and there is a certain 
ft correspondence bet 
