flesh-cells, blood-cells,
brain-cells, and so on, adapting themselves to the different organs they
are to build up; but they have as much their definite and appointed
share in the formation of the body now as at any later stage of its
existence.

We are so accustomed to see life maintained through a variety of
complicated organs that we are apt to think this the only way in which
it can be manifested; and considering how closely life and the organs
through which it is expressed are united, it is natural that we should
believe them inseparably connected. But embryological investigations
have shown us that in the commencement none of these organs are formed,
and yet that the principle of life is active, and that even after they
exist, they cannot act, inclosed as they are. In the little Chicken, for
instance, before it is hatched, the lungs cannot breathe, for they
are surrounded by fluid, the senses are inactive, for they receive no
impressions from without, and all those functions establishing its
relations with the external world lie dormant, for as yet they are not
needed. But they are there, though, as we have seen in the Turtle's egg,
they were not there at the beginning. How, then, are they formed? We may
answer, that the first function of every organ is to make itself. The
building material is, as it were, provided by the process which divides
the yolk into innumerable cells, and by the gradual assimilation and
modification of this material the organs arise. Before the lungs
breathe, they make themselves; before the stomach digests, it makes
itself; before the organs of the senses act, they make themselves;
before the brain thinks, it makes itself; in a word, before the whole
system works, it makes itself; its first office is self-structure.

At the period described above, however, when the new generations of
cells are just set free and have taken their place in the region where
the new being is to develop, nothing is to be seen of the animal whose
life is beginning there, except the filmy disk lying on the surface of
the yolk. Next come the layers of white or albumen around the egg, and
last the shell which is formed from the lime in the albumen. There is
always more or less of lime in albumen, and the hardening of the last
layer of white into shell is owing only to the greater proportion of
lime in its substance. In the layer next to the shell there is enough of
lime to consolidate it slightly, and it forms a