the
ordinary method of their propagation in any other respect than this,
that in both cases the result is brought about by Natural Laws, without
the direct interposition of any supernatural cause.

Now, in so far as his argument is founded on the principle of
analogy,--and it is on this principle that it proceeds throughout,--we
submit that it is radically vicious, and utterly inconclusive. For the
vast majority of cases in which the commencement of life and
organization falls under our notice being confessedly those, not of
primary production, but of mediate reproduction, it is reasonable to
believe that the same law governs all cases alike, whether we have been
able or not to trace the origin of life to the principle of propagation,
the few apparent exceptions being sufficiently accounted for by our
imperfect knowledge of the causes and conditions on which they depend.
Besides, the argument from analogy in favor of a primary production of
life by natural causes, in so far as it is founded on the present law
of hereditary transmission, is radically defective, since the two cases
are widely different; the one presupposing _a primary organism of the
same kind_, from which others are evolved by a law of natural
succession, the other exhibiting life as a new product, resulting not
from any prior organism, but from the action of _causes of a totally
different kind_, which are not known to be capable of giving birth
either to vegetable or animal organisms under the actual constitution of
Nature.

But suppose, even, that the _Acarus Crossii_ were admitted to be a real
product of Galvanic action on the silicate of potash, and an undeniable
instance of "a non-generative origin of life," how would the
illustrative example accord with the author's general theory? It might
afford a specimen of aboriginal production; but how would it fit in with
his favorite doctrine of _a gradual and progressive advancement_ from
the lower to the higher forms of organization? The _Acarus_, at first
supposed to be a new and hitherto unknown creature, is now acknowledged
to be one of a very familiar species,--a species which may have
deposited its ova, and propagated its kind, since the commencement of
the present order of things, and whose eggs might very well resist the
action even of nitrate of copper, since the creature itself could live
in that poisonous mixture. Moreover, it belongs, in point of
organization, to one of the highest orders of