eing now of special use to the descendants
of this form--either directly, or indirectly, through the complex
laws of growth."

But it is one thing to say, Darwinically, that every detail observed in
an animal's structure is of use to it, or has been of use to its
ancestors; and quite another to affirm, teleologically, that every
detail of an animal's structure has been created for its benefit. On the
former hypothesis, for example, the teeth of the foetal _Balaena_ have
a meaning; on the latter, none. So far as we are aware, there is not a
phrase in the "Origin of Species," inconsistent with Professor
Koelliker's position, that "varieties arise irrespectively of the notion
of purpose, or of utility, according to general laws of Nature, and may
be either useful, or hurtful, or indifferent."

On the contrary, Mr. Darwin writes (Summary of Chap. V.):--

"Our ignorance of the laws of variation is profound. Not in one
case out of a hundred can we pretend to assign any reason why this
or that part varies more or less from the same part in the
parents.... The external conditions of life, as climate and food,
&c. seem to have induced some slight modifications. Habit, in
producing constitutional differences, and use, in strengthening,
and disuse, in weakening and diminishing organs, seem to have been
more potent in their effects."

And finally, as if to prevent all possible misconception, Mr. Darwin
concludes his Chapter on Variation with these pregnant words:--

"Whatever the cause may be of each slight difference in the
offspring from their parents--and a cause for each must exist--it
is the steady accumulation, through natural selection of such
differences, when beneficial to the individual, that gives rise to
all the more important modifications of structure, by which the
innumerable beings on the face of the earth are enabled to struggle
with each other, and the best adapted to survive."

We have dwelt at length upon this subject, because of its great general
importance, and because we believe that Professor Koelliker's criticisms
on this head are based upon a misapprehension of Mr. Darwin's
views--substantially they appear to us to coincide with his own. The
other objections which Professor Koelliker enumerates and discusses are
the following:[66]--

"1. No transitional forms between existing species are known; and
known