animal--are only apparent. These creatures, which are low down in the
scale of being, exemplify what Mr. Owen calls "the law of vegetative or
irrelative repetition," as they have many organs performing the same
function, and not related to each other by combination for the
performance of a higher function. Thus, a Polygastrian has many
assimilative sacs, each performing the office of a stomach irrespective
of the rest. In the insect tribe, the respiratory function, instead of
being performed by one set of lungs for the whole body, is carried on
through a series of minute and highly ramified tubes, which traverse
every part of the body, and open to the air by a great number of
orifices. In some instances, both respiration and digestion seem to take
place over the whole surface of the body; for Trembley found at least
one case, in which the animal digested its food equally well, after it
had been turned inside out. A number of similar parts being repeated in
each segment of the individual, the body can be divided, and the several
portions, each still containing some of all the organs essential to the
whole, will continue to live separately. The severed parts will even
continue to grow, and to develope other organs convenient for individual
existence. But most animals, especially the more perfect, do not
constitute an aggregate of similar parts united by one trunk, and
therefore propagation by division is in them impossible. The ovum, when
separated from the parent, is an entire animal only _potentially_;
during its development, the essential parts which constitute the
_actual_ whole are produced. In the case of the polyps, we have only to
suppose that the ovum remains connected with the parent being, till all,
or nearly all, its essential parts are produced. It is then shed not as
a mere ovum, but as an animal nearly or wholly complete.

Now, all the instances adduced by our author, to show similarity of
action in the organic and the inorganic world, are irrelevant. The
analogies are not merely imperfect; they are no analogies at all.
Crystals increase by the aggregation of new particles on the external
surfaces of the parts already formed; there is no consentaneous
operation of the parts on the whole. The molecules of crystals are
homogeneous throughout, and the several aggregates of these molecules
are independent of each other; while organized bodies are composed of
parts perfectly dissimilar from each other, but all of