"On the one hand, it cannot be in those proximate chemical compounds composing organic bodies, that this specific polarity dwells. It cannot be that atoms of albumen, or fibrine, or gelatine, or the hypothetical protein substance, possess this power of aggregating into specific shapes, for in such cases there would be nothing to account for the unlikenesses of different organisms. Millions of species of plants and animals, more or less contrasted in their structures, are all mainly built up of these atoms. But if the polarities of these atoms determined the forms of the organisms they composed, the occurrence of such endlessly varied forms would be inexplicable. Hence, what we may call the chemical units are clearly not the possessors of this property.
"On the other hand, this property cannot reside in what may roughly be distinguished as the morphological units. The germ of every organism is a microscopic cell. It is by multiplication of cells that all the early developmental changes are affected. The various tissues which successively arise in the unfolding organism, are primarily cellular, and in many of them the formation of cells continues to be, throughout life, the process by which repair is carried on. But though cells are so generally the ultimate visible components of organisms, that they may, with some show of reason, be called the morphological units; yet, as they are not universal, we cannot say that this tendency to aggregate into specific forms, dwells in them. Finding that in many cases a fibrous tissue arises out of a structureless blastema without cell formation, and finding that there are creatures, such as the Rhizopods, which are not cellular, but nevertheless exhibit vital activities, and perpetuate in their progeny certain specific distinctions, we are forbidden to ascribe to cells this peculiar power of arrangement. Nor, indeed, were cells universal, would such an hypothesis be acceptable, since the formation of a cell is, to some extent, a manifestation of this peculiar power.
"If, then, this organic polarity can be possessed neither by the chemical units nor by the morphological units, we must conceive it as possessed by certain inter-