into the active state.

Thus, so far as outward form and the general character of the cycle of
modifications, through which the organism passes in the course of its
life, are concerned, the resemblance between _Chlamydomonas_ and
_Heteromita_ is of the closest description. And on the face of the matter
there is no ground for refusing to admit that _Heteromita_ may be related
to _Chlamydomonas_, as the colourless fungus is to the green alga.
_Volvox_ may be compared to a hollow sphere, the wall of which is made up
of coherent Chlamydomonads; and which progresses with a rotating motion
effected by the paddling of the multitudinous pairs of cilia which
project from its surface. Each _Volvox_-monad, moreover, possesses a red
pigment spot, like the simplest form of eye known among animals. The
methods of fissive multiplication and of conjugation observed in the
monads of this locomotive globe are essentially similar to those observed
in _Chlamydomonas_; and, though a hard battle has been fought over it,
_Volvox_ is now finally surrendered to the Botanists.

Thus there is really no reason why _Heteromita_ may not be a plant; and
this conclusion would be very satisfactory, if it were not equally easy
to show that there is really no reason why it should not be an animal.
For there are numerous organisms presenting the closest resemblance to
_Heteromita_, and, like it, grouped under the general name of "Monads,"
which, nevertheless, can be observed to take in solid nutriment, and
which, therefore, have a virtual, if not an actual, mouth and digestive
cavity, and thus come under Cuvier's definition of an animal. Numerous
forms of such animals have been described by Ehrenberg, Dujardin, H.
James Clark, and other writers on the _Infusoria_. Indeed, in another
infusion of hay in which my _Heteromita lens_ occurred, there were
innumerable such infusorial animalcules belonging to the well-known
species _Colpoda cucullus_.[6]

[Footnote 6: Excellently described by Stein, almost all of whose
statements I have verified.]

Full-sized specimens of this animalcule attain a length of between 1/300
or 1/400 of an inch, so that it may have ten times the length and a
thousand times the mass of a _Heteromita_. In shape, it is not altogether
unlike _Heteromita_. The small end, however, is not produced into one
long cilium, but the general surface of the body is covered with small
actively vibrating ciliary organs, which are only longest at th