cur to which the comparatively immobile organism finds itself
structurally unable to respond. Thus a _Medusa_ tossed ashore by a wave,
finds itself so out of correspondence with its new surroundings that its
life must pay the forfeit. Had it been able by internal change to adapt
itself to external change--to correspond sufficiently with the new
environment, as for example to crawl, as an eel would have done, back
into that environment with which it had completer correspondence--its
life might have been spared. But had this happened it would continue to
live henceforth only so long as it could continue in correspondence with
all the circumstances in which it might find itself. Even if, however,
it became complex enough to resist the ordinary and direct dangers of
its environment, it might still be out of correspondence with others. A
naturalist for instance, might take advantage of its want of
correspondence with particular sights and sounds to capture it for his
cabinet, or the sudden dropping of a yacht's anchor or the turn of a
screw might cause its untimely death.

Again, in the case of a bird, in virtue of its more complex
organization, there is command over a much larger area of environment.
It can take precautions such as the _Medusa_ could not; it has increased
facilities for securing food; its adjustments all round are more
complex; and therefore it ought to be able to maintain its Life for a
longer period. There is still a large area, however, over which it has
no control. Its power of internal change is not complete enough to
afford it perfect correspondence with all external changes, and its
tenure of Life is to that extent insecure. Its correspondence, moreover,
is limited even with regard to those external conditions with which it
has been partially established. Thus a bird in ordinary circumstances
has no difficulty in adapting itself to changes of temperature, but if
these are varied beyond the point at which its capacity of adjustment
begins to fail--for example, during an extreme winter--the organism
being unable to meet the condition must perish. The human organism, on
the other hand, can respond to this external condition, as well as to
countless other vicissitudes under which lower forms would inevitably
succumb. Man's adjustments are to the largest known area of Environment,
and hence he ought to be able furthest to prolong his Life.

It becomes evident, then, that as we ascend in the scale of Life