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