Page:Popular Science Monthly Volume 3.djvu/575

Rh steps all move toward the same end, which is, the functional action of the organism, and the perpetuation of the species.

What takes place in the ovule is a miniature image of what takes place in the universe. The differentiations occurring in that mucous drop are a copy of the differentiations unfolding and expanding in the ocean of the world. It is at first a microscopic mass, homogeneous, uniform in all its parts, a collection of energies identical with each other, and the group of which does not differ perceptibly from a drop of gelatine, hanging, hardly seen, from a needle's point. Yet soon a dull motion spontaneously stirs these nearly inert atoms, and this motion is expressed by a first condensation of the ovular or vitelline substance, which is the germinating vesicle. This passes off, but at the same time other vibrations arrange the molecules of this shapeless, transparent microcosm, in the order of more complicated groups. The vitelline substance swells toward the surface, where it forms the polar globules, while at the centre it thickens to produce the vitelline nucleus. This in turn cleaves and breaks into a great number of secondary nuclei, around each of which the ovular mass distributes itself while contracting. Instead of a single cell, the ovule, which has enlarged, is now found to contain a great number. These cells, called blastodermic, then tend to arrange themselves in two layers, two leaflets placed back to back, within which the elements of the embryo appear, and little by little develop, pursuing a continuous growth, in which forces becoming forms go on incessantly producing and multiplying new forces and new forms.

Now, these separations and distributions, these orderings and classifyings, these harmonies that are set up in the ovule to compose by slow degrees the structure of the embryo, reveal a principle of differentiation analogous to that which has caused the infinite variety of things we see come forth from the confused mass of cosmic energies. There is, as many biologists had felt assured, and as Coste has had the glory of clearly demonstrating in a work which is one of the noblest scientific monuments of this age, there is a force which gives reality, direction, life, to the forms of organized matter in the egg. All eggs are alike at first. There is a complete similitude in structure and substance between those which will produce a lion and those which will produce a mouse. The forms are identical, though the future of those forms is different. It is, as Coste very well says, that "beneath that form, and beyond what the eye views, there is something which sight cannot reach, something which contains in itself the sufficient reason for all those differences now concealed under unity of configuration, and to become visible only later." This guiding idea, which Coste has brought forward, and which is admitted by all physiologists at this day, is as far from issuing out of the elementary forces of nutrition as the painter's picture is from being the creature of his palette. Yet nothing in the ovule reveals its hidden and