, the facts of the case, so far as the skate is
concerned, assuredly do appear to sanction the doctrine of "prophetic
germs." The organ in the skate seems to be on its way towards becoming
such an organ as we meet with in these other animals; and, therefore,
unless we can show that it is now, and in all previous stages of its
evolution has throughout been, of use to the skate, the facts do present
a serious difficulty to the theory of natural selection, while they
readily lend themselves to the interpretation of a disposing or
fore-ordaining mind, which knows how to construct an electric battery by
thus transforming muscular tissue into electric tissue, and is now
actually in process of constructing such an apparatus for the
prospective benefit of future creatures.
Should it be suggested that possibly the electric organ of the skate may
be in process of degeneration, and therefore that it is now the
practically functionless remnant of an organ which in the ancestors of
the skate was of larger size and functional use--against so obvious a
suggestion there lie the whole results of Professor Ewart's
investigations, which go to indicate that the organ is here not in a
stage of degeneration, but of evolution. For instance, in _Raia
radiata_, it does not begin to be formed out of the muscular tissue
until some time after the animal has left the egg-capsule, and assumed
all the normal proportions (though not yet the size) of the adult
creature. The organ, therefore, is one of the very latest to appear in
the ontogeny of _R. radiata_; and, moreover, it does not attain its full
_development_ (i. e. not merely _growth_, but transforming of muscular
fibres into electrical elements) till the fish attains maturity. Read in
the light of embryology, these facts prove, (1) that the electric organ
of _R. radiata_ must be one of the very latest products of the
animal's phylogeny; and, (2) that as yet, at all events, it has not
begun to degenerate. But, if not, it must either be at a stand-still, or
it must be in course of further evolution; and, whichever of these
alternatives we adopt, the difficulty of accounting for its present
condition remains. In this connexion also it is worth while to remark
that the electric organ, even after it has attained its full
_development_, continues its _growth_ with the growth of the fish, and
this in a much higher ratio, either than the tail alone, or the whole
animal. Lastly, Prof. Burdon Sanderson
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