primordial form of a single cell. 

We found that our analysis of the organic world, whether animals or
plants, showed, in the long run, that they might both be reduced into,
and were, in fact, composed of, the same constituents.  And we saw that
the plant obtained the materials constituting its substance by a
peculiar combination of matters belonging entirely to the inorganic
world; that, then, the animal was constantly appropriating the
nitrogenous matters of the plant to its own nourishment, and returning
them back to the inorganic world, in what we spoke of as its waste; and
that finally, when the animal ceased to exist, the constituents of its
body were dissolved and transmitted to that inorganic world whence they
had been at first abstracted.  Thus we saw in both the blade of grass
and the horse but the same elements differently combined and arranged.
We discovered a continual circulation going on,--the plant drawing in
the elements of inorganic nature and combining them into food for the
animal creation; the animal borrowing from the plant the matter for its
own support, giving off during its life products which returned
immediately to the inorganic world; and that, eventually, the
constituent materials of the whole structure of both animals and plants