THE
ASYMMETRY OF THE CYCLE OF LIFE 159
and
plants merge together, and that some of the lower organisms may be described
equally well as animals or as plants? The scientific truth of the matter is
that there is no merging together of the two kingdoms. Such a blending is
impossible, because of the asymmetrical carbon atom. None the less, the
asymmetrical carbon atom vouches the unity of organic nature.
It
is clear that, if in any group of organisms, animals, plants, bacteria, fungi,
etc., there be two phases of the life-cycle, asexual and sexual, there are for
any given case two directions in which the naturally occurring organic
compounds can be built up. But it should not be forgotten that the number of
possible isomeric compounds increases with their complexity. The sexual
generation of animals is characterized by dextro-sugars, dextro-glycogen, and
laevo-albumins. In the corresponding sexual generation of plants, such as the
fern prothallus, these are absent, being replaced by enantiomorphous compounds
with the opposite rotations. It is the asexual generation of plants, the
flowering plant, and not the sexual generation, which possesses dextro-sugar,
dextro-starch, and laevo-albumins. The harmony of this is twofold. It realizes
the apparent possibilities, and from the point of view of animal life it is of
overwhelming importance that it should be so. Ultimately, of course, all
animals are dependent on plants for their foodstuffs. Were the sexual
generations of plants the producers of the foodstuffs of animals, the latter,
owing to the insignificance of the former, would find existence a very serious
problem. The sexual generations of plants form substances resembling those
fabricated by the asexual generations of animals, trophoblast, or cancer. Even
if obtainable in sufficiently large quantities, the substances found naturally
in a cancer would not be suitable as the