haracter, as recorded by Fritz
Muller, after maturity. In all such cases--and many could be given--if
the age for reproduction were retarded, the character of the species, at
least in its adult state, would be modified; nor is it improbable that
the previous and earlier stages of development would in some cases be
hurried through and finally lost. Whether species have often or ever
been modified through this comparatively sudden mode of transition, I
can form no opinion; but if this has occurred, it is probable that the
differences between the young and the mature, and between the mature and
the old, were primordially acquired by graduated steps.

SPECIAL DIFFICULTIES OF THE THEORY OF NATURAL SELECTION.

Although we must be extremely cautious in concluding that any organ
could not have been produced by successive, small, transitional
gradations, yet undoubtedly serious cases of difficulty occur.

One of the most serious is that of neuter insects, which are often
differently constructed from either the males or fertile females; but
this case will be treated of in the next chapter. The electric organs of
fishes offer another case of special difficulty; for it is impossible
to conceive by what steps these wondrous organs have been produced. But
this is not surprising, for we do not even know of what use they are.
In the gymnotus and torpedo they no doubt serve as powerful means of
defence, and perhaps for securing prey; yet in the ray, as observed
by Matteucci, an analogous organ in the tail manifests but little
electricity, even when the animal is greatly irritated; so little that
it can hardly be of any use for the above purposes. Moreover, in the
ray, besides the organ just referred to, there is, as Dr. R. McDonnell
has shown, another organ near the head, not known to be electrical, but
which appears to be the real homologue of the electric battery in the
torpedo. It is generally admitted that there exists between these organs
and ordinary muscle a close analogy, in intimate structure, in the
distribution of the nerves, and in the manner in which they are acted
on by various reagents. It should, also, be especially observed that
muscular contraction is accompanied by an electrical discharge; and,
as Dr. Radcliffe insists, "in the electrical apparatus of the torpedo
during rest, there would seem to be a charge in every respect like that
which is met with in muscle and nerve during the rest, and the discharge
of the tor