THE CONSTITUTION OF MATTER. 21 
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 num- 
ber. 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 order- 
ings 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 iden- 
tical, though the futures of those forms differ. 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, 
