Page:George Archdall Reid 1896 The present evolution of man.djvu/79

Rh living organisms, is the same as that which causes, under fit conditions, the growth of crystals. Under fit conditions a crystal grows into a definite shape, according to its kind, and so does an organism; but there the analogy ends. Mr. Spencer, with more reason, might have compared an organism to a river, and reasoned from that basis. A river grows like a crystal and an organism, but, like an organism and unlike a crystal, waxes and wanes according to circumstances, is somewhat heterogeneous in composition, consists from time to time of new material, and so forth.

A crystal is essentially stable and homogeneous throughout, and if in a solution there are molecules of different kinds capable of crystallization, they crystallize separately into different kinds of crystals. "Our very definition of crystal structure is an arrangement of particles, the same about one point as about every other point; hence, in one sense, the smallest fragment of a crystal is complete in itself."

An organism is essentially unstable and heterogeneous; the lowest organisms we are able to examine show in their granular appearance unmistakable evidence of heterogeneity; higher organisms are obviously heterogeneous, and, according to Mr. Spencer, the physiological visits in them must, if they have any existence, be highly heterogeneous, since he speaks of the "specialized molecules of each organ" (Principles of Biology, vol. i. p. 178), though here he does not explain by what process of crystallization the molecules of a crystal are "specialized"; since he speaks of "countless different combinations of units derived from parents, and through them from ancestors immediate and remote" (p. 268); and since he speaks of "the mixed physiological units composing any organism, being, as we have seen (?),