1889.] Ojt Inheritance in Evolution. 1059 
In the first place, no sharp and fast line can be drawn between 
" congenital " and " acquired " characters. It has not been shown 
that the former have not been acquired at an early period, and 
become by long use incorporated into the organism so as to 
constitute an essential part of it. It is highly probable that it is 
just this use which is the index of the value of a character, — which 
has rendered characters, at first feebly acquired, finally congenital 
in the fullest sense. The vast majority of mutilations are not 
useful, and are not generally frequently repeated in the history of 
a phylogenetic line, so that they are never sufficiently impressed 
on the organism to become congenital. It is evident that the 
kind of characters which have become such, are those which result 
from use in the fullest sense of the word ; that is, by countless 
repetitions continued for immense periods of time. This is clearly 
the case with respect to the movements of animals which are 
necessary to their progress through the mediums in which they 
live ; to the obtaining of their food, and to the propagation of their 
kind. These have been indefinitely repeated, and their mechanical 
effects on the hard supports of the body, as the skeleton, external 
and internal, and on the protoplasm whose contractions move the 
skeleton, were repeated by successive generations before they were 
inherited, and were by degrees incorporated into the growth- 
habit of the type, or became, in other w^ords, congenital and inher- 
itable. Such is the hypothesis of inheritance as affecting and 
effecting progressive evolution ; and it is difficult to believe that 
it is not true. We see much of inheritance about us. The char- 
acters which are now inherited have not always existed, and they 
must have been acquired at some time or another. 
It has been shown by Brooks that bisexual reproduction, by 
doubling the sources of inheritance, doubles the opportunities for 
variation of characteristics in descent. This has led Weismann 
and others to trace all variation to this source. That this propo- 
sition is quite insufficient to explain the origin of variation is evi- 
dent on slight consideration. The appeal to inheritance as a 
source of variation, no matter whether the inheritance be simple 
(unisexual) or complex (bisexual) explains nothing. The varia- 
tions originated at a definite time and in a definite place, whether 
