in color. Now, the red rays of the
spectrum are the ones which are most efficient for photosynthesis. Sea
weeds which grow at these depths are brilliantly red in color, at
intermediate depths they are brown, and at the surface they are green, in
the same latitudes. While it is possible that the temperature of the water
at these different depths may have something to do with the chemical
synthesis of the pigments, it appears plain that this color change at
increasing depths is a definite adaptation to provide for the absorption of
the solar energy which is available at these depths. It has been shown that
these pigments of deep-sea plants are additional to, and not substitutes
for, the chlorophylls, etc. The latter pigments are present in normal
amounts, but are supplemented by those which absorb the green and blue
portion of the spectrum. Hence, this type of adaptation might be conceived
to be a "survival of the fittest," resulting in the "natural selection" of
individuals of the highest total pigmentation. But, on the other hand,
there is experimental evidence to show that plants possess some means of
varying their pigmentation in response to the character of the light which
comes to them. For, it has been found that a complete change in color of
certain highly colored plants can be produced in a single generation, by
growing the plants in boxes or chambers whose walls are composed entirely
of differently colored glass, so that the plants within receive light of
only a particular part of the spectrum. In such cases, the plant, starting
with an initial "natural" color, changes through a succession of colors
until it finally reaches equilibrium at one which provides for the proper
absorption of the right kind of light from the new supply which is
available to it. Hence, it seems proper to conclude that chromatic
adaptation is not a process of "natural selection," but a definite result
of an actual mechanism for adaptation to changed environmental conditions
of supply of radiant energy.

STRUCTURAL ADAPTATIONS

Changes in structure to meet special conditions of growth may be of several
different types.

One of these, which is often cited as an example of adaptation (in this
case, the term is used with a significance quite different than that in
which it is being used here) is that of the development of unusual and
often fantastic shapes of flowers, which are so related to the anatomy of
cert