THE ASYMMETRY OF THE CYCLE OF LIFE 153
cellulose, or a laevo-albumin, or a dextro-sugar, or a dextro-glycogen, stereo-chemistry asserts the possibility, or the necessity, of the occurrence of a laevo-cellulose, a dextro-albumin., a laevo-sugar, a laevo-glycogen. This the reader will find laid down on p. 14. of Meyerhoffer’s German translation of van ‘t Hoff’s work. Duclaux* rightly observes that to obtain the change from the one direction of asymmetry to the other, it is necessary to go back to the “germ.” Like the cellulose of a flowering plant, a rose or an oak-tree, that of the fern-plant is dextro-cellulose. But in the life-cycle of the fern, as in that of the flowering plant, there are two generations, the asexual one, or fern-plant, and the sexual one, the small and insignificant prothallus. As the cellulose of the fern is dextro-cellulose, so that of the latter must be laevo-cellulose, and so with the other naturally occurring organic compounds. None such found naturally in an asexual generation of a plant, or in a sexual generation of an animal, will be met with in the corresponding sexual generation of a plant or asexual generation of an animal; but, if occurring at all, it will be represented by a compound with the opposite rotation. The reason is because (like the pentavalent nitrogen one) there is an asymmetrical carbon atom.
(cont from p 152) governing the whole long series.” He dilates on “the grand picture which Hofmeister had drawn up of the genetic connections of the members of the Plant Kingdom.” What the zoologists were to experience fifty years later—viz., an antithetic alternation of generations in animals as the law of their developmental cycles, was unravelled for plants by Wilhelm Hofmeister. nine years before Pasteur gave the two lectures “ On the Asymmetry of the Naturally Occurring Organic Compounds,” and before he uttered the prophetic words, “ Who can foresee the organization that living matter would assume, if cellulose were laevo-rotatory instead of being dextro-rotatory ?“
* Duclaux, E.: “Pasteur, Histoire d’un Esprit,” Paris, 1896, pp. i-vii and 1-393.