f the cause: the effect is invariable.
In the third, the quantity of the effect depends on the quantity of the
cause, but the cause does not influence the quality of the effect: the
longer the cylinder turns by the action of the spring, the more of the
melody I shall hear, but the nature of the melody, or of the part heard,
does not depend on the action of the spring. Only in the first case,
really, does cause _explain_ effect; in the others the effect is more or
less given in advance, and the antecedent invoked is--in different
degrees, of course--its occasion rather than its cause. Now, in saying
that the saltness of the water is the cause of the transformations of
Artemia, or that the degree of temperature determines the color and
marks of the wings which a certain chrysalis will assume on becoming a
butterfly, is the word "cause" used in the first sense? Obviously not:
causality has here an intermediary sense between those of unwinding and
releasing. Such, indeed, seems to be Eimer's own meaning when he speaks
of the "kaleidoscopic" character of the variation,[33] or when he says
that the variation of organized matter works in a definite way, just as
inorganic matter crystallizes in definite directions.[34] And it may be
granted, perhaps, that the process is a merely physical and chemical one
in the case of the color-changes of the skin. But if this sort of
explanation is extended to the case of the gradual formation of the eye
of the vertebrate, for instance, it must be supposed that the
physico-chemistry of living bodies is such that the influence of light
has caused the organism to construct a progressive series of visual
apparatus, all extremely complex, yet all capable of seeing, and of
seeing better and better.[35] What more could the most confirmed
finalist say, in order to mark out so exceptional a physico-chemistry?
And will not the position of a mechanistic philosophy become still more
difficult, when it is pointed out to it that the egg of a mollusc cannot
have the same chemical composition as that of a vertebrate, that the
organic substance which evolved toward the first of these two forms
could not have been chemically identical with that of the substance
which went in the other direction, and that, nevertheless, under the
influence of light, the same organ has been constructed in the one case
as in the other?

The more we reflect upon it, the more we shall see that this production
of the same effect by