134 ANIMAL PHYSIOLOGY. 
structural change. From our conceptions of the nature of liv- 
ing matter, it naturally follows that variation should be great- 
est, as has been observed, under the greatest alteration in the 
surroundings. 
We are but very imperfectly acquainted as yet with the 
conditions under which life existed in the earlier epochs of the 
earth’s history. Of late, deep-sea soundings and arctic explo- 
rations have brought surprising facts to light, showing that 
living matter can exist under a greater variety of conditions 
than was previously supposed. Thus it turns out that light is 
not an essential for. life everywhere. We think these recent 
revelations of unexpected facts should make us cautious in as- 
suming that life always manifested itself under conditions 
closely similar to those we know. Variation may at one period 
have been more sudden and marked than Darwin supposes; 
and there does seem to be room for such a conception as the 
“extraordinary births” of Mivart implies; though we would not 
have it understood that we think Darwin’s view of slow modi- 
fication inadequate to produce a new species; we simply vent- 
ure to think that he was not justified in insisting so strongly 
that this was the only method of Nature; or, to put it more 
justly for the great author of the “ Origin of Species,” with the 
facts that have accumulated since his time he would scarcely 
be warranted in maintaining so rigidily his conviction that 
new forms arose almost exclusively by the slow process he has 
so ably described. 
As there must be all degrees in consciousness, we do not 
deny that it may be logical to assume some dim spark of this 
quality in all protoplasm, as Cope insists; and that it plays a 
part in determining action and growth there seems to be no 
doubt. But is it not more philosophical to regard conscious- 
ness and all allied qualities as correlatives, and underlaid by a 
molecular constitution with which it is associated as other qual- 
ities ? It is unduly exalted in the neo-Lamarckian philosophy. 
We must allow a great deal to use and effort, doubtless, and 
they explain the origin of variations up to a certain point, but 
the solution is only partial. Variations must arise as we have 
attempted to explain, and use and disuse are only two of the 
factors amid many. Correlated growth, or the changes in one 
part induced by changes in another, is a principle which, though 
recognized by Darwin, Cope, and others, has not, we think, re- 
ceived the attention it deserves. To the mind of the physiolo- 
gist, all changes must be correlated with others. 
