at changes.

If, therefore, our author, guided by this illustration of Mr Babbage's,
proclaims a law of animal life which _changes of itself_ from time to
time, he is departing from the fundamental principle of all science--he
who is so zealous to reduce all phenomenon to the formula of science!
Anxious to escape from an abrupt interposition of creative power, he
introduces a sudden mutability in the laws themselves of nature! If it be
said that he does not (although his words imply it) insist upon a single
law of nature that varies at intervals, but contends for a variable
result, produced by the law of reproduction acting under varied
circumstances, and in co-operation with different laws--then was Mr
Babbage's machine of no use whatever to him, nor did he stand in need of
any peculiar illustration. There is not a class of phenomena which does
not exhibit this variety of result by the diversified co-operation of laws
constant in themselves. The frozen river becomes motionless; it ceases to
flow; yet no one attributes any inconstancy to the laws of heat, or the
laws of hydrostatics.

Quitting these abstractions, in which the writer before has shown himself
no very great adept, let us enquire by what arguments he attempts to
support his peculiar _principles of development_. That on which he appears
chiefly to rely is the fact, that the embryo of one of the higher animals
passes through the foetal stages of the lower animals--the fish, the
reptile, the bird--before it assumes its last definite shape. From this he
would infer, that the germ of life is alike in all, and that it depends
only on peculiarities of gestation whether it shall become a fish, a fowl,
or a mammal. He lays particular stress on the circumstance, that the brain
of the human embryo passes through these several stages.

But, 1. In order to derive any thing like an argument here, surely the
whole human embryo, and not the brain only, ought to undergo these
changes. But not only in man, in the other mammalia to which allusion is
made, it is never the _entire animal_ which passes through these
transformations.

2. If the embryo of one of the mammalia pass through the foetal stages
of the fish and the bird, the embryo fish bears the same transitory
resemblance to the foetal condition of the bird or the mammal. So that
the order here is reversed, and nothing appears proved but that some
deviations of form are in all cases assumed before the final shape is