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transformed into a gill-less newt, long known as an American genus,
and named Amblystoma. . . . By careful experimentation, a lady
naturalist, Fraiilein von Chauvin, showed that by gradually inuring
the axolotl first to a life among damp moss and then to an existence
entirely removed from the water, it could be made to assume the
amblystoma form, with its black skin and yellow spots. . . . It is
obvious that this treatment must be applied very gradually and in
such a manner as not to overtax the vital energy of the amphibian.”
—(Dr. Andrew Wilson. Chapters on Evolution, pp. 24.2-3.)
Two explanations of this phenomenon are possible. It
may be said that the axolotl represents the larval stage
of the amblystoma—one branch of the amblystoma race
never having got beyond that stage of evolution ; or it
may be said that the axolotl is the degenerate form of
the amblystoma. Now, if the case of the frog may be
regarded as analogous, it seems probable that the axolotl
is a larval form of the amblystoma. No one, I suppose,
doubts that the frog is descended from ancestors which
once lived as fishes, and as newts before they became
frogs, and which handed down their distinctive charac
teristics from generation to generation. But if the frog
had been born a frog, and if nothing had been known
concerning the history of the race until a tadpole had
been for the first time seen to be metamorphosed into a
frog, it might then have been an open question whether
the frog were a larval or a degenerate form.
Certain reasons are, however, assigned for the belief that
the axolotl is actually a retrogressive form of amblystoma.
Dr. Weismann maintains that the case in question is one
not of sudden advance in a species, but of reversion to a
lower stage.
“ I believe that the axolotls which now inhabit the Mexican lakes
were amblystomas at a former geological (or, better, zoological) epoch,
but that owing to changes in their conditions of life, they have
reverted to the earlier permanently-gilled stage.”—(Apud Wilson.
p. 248.)
