that is widespread and vociferous.

To Weismann more than to any other single individual should be ascribed the
disfavor into which this view has fallen. In a series of brilliant essays
he laid bare the inadequacy of the supposed evidence on which the
inheritance of acquired characters rested. Your neighbor's cat, for
instance, has a short tail, and it is said that it had its tail pinched off
by a closing door. In its litter of kittens one or more is found without a
tail. Your neighbor believes that here is a case of cause and effect. He
may even have known that the mother and grandmother of the cat had natural
tails. But it has been found that short tail is a dominant character;
therefore, until we know who was the father of the short-tailed kittens the
accident to its mother and the normal condition of her maternal ancestry is
not to the point.

Weismann appealed to common sense. He made few experiments to disprove
Lamarck's hypothesis. True, he cut off the tails of some mice for a few
generations but got no tailless offspring and while he gives no exact
measurements with coefficients of error he did not observe that the tails
of the descendants had shortened one whit. The combs of fighting cocks and
the tails of certain breeds of sheep have been cropped for many generations
and the practice continues today, because their tails are still long. While
in Lamarck's time there was no evidence opposed to his ingenious theory,
based as it was on an appeal to the acknowledged facts of improvement that
take place in the organs of an individual through their own functioning (a
fact that is as obvious and remarkable today as in the time of Lamarck),
yet now there is evidence as to whether the effects of use and disuse are
inherited, and this evidence is not in accord with Lamarck's doctrine.

THE UNFOLDING PRINCIPLE

_Naegeli and Bateson_

I have ventured to put down as one of the four great historical
explanations, under the heading of the unfolding principle, a conception
that has taken protean forms. At one extreme it is little more than a
mystic sentiment to the effect that evolution is the result of an inner
driving force or principle which goes under many names such as
Bildungstrieb, nisus formativus, vital force, and orthogenesis.
Evolutionary thought is replete with variants of this idea, often naively
expressed, sometimes unconsciously implied. Evolution once meant, in fact,
an unfolding of what pre-existed in the