We easily
fail to notice it; and, unless we take a careful view of the course
of development in the highest forms of life, we may be inclined to
deny its existence. But it is surely there, if man is a product of
evolution.
Each successive stage of animal life is not the preceding stage on a
higher plane, but the preceding stage modified in conformity to the
environment of that from which it has just arisen. Says Professor
Hertwig[A]: "During the process of organic development the external
is continually becoming an integral part of the individual. The germ
is continually growing and changing at the expense of surrounding
conditions." Every stage thus contains the result of a host of
reactions to a ruder and older portion of environment. And the
higher we go the more has the original protoplasm and structure been
modified as the result of these reactions.
[Footnote A: Hertwig: Zeit- und Streitfragen, p. 82.]
We have seen clearly that environment must be studied through its
effect upon living beings. Viewed from any other standpoint it
appears to be a myriad, almost a chaos, of interacting, apparently
conflicting, forces. The resultant of some of these is shown by the
animal at any stage of its development. And as the animal advances,
the resultant determining its new line, or stage, of advance,
includes new forces, to which it has only lately become sensitive.
Pages:
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262