The American Naturalist. 
ON INHERITANCE IN EVOLUTION. 
BY E. D. COPE. 
T^HE hypothesis of evolution rests on the fact that the character 
possessed by one generation of animals and plants may be 
inherited by descendants. In the case of retardation, retrograde 
metamorphosis, or degeneracy, certain characters are lost by the 
failure to be inherited. In the case of stationary or persistent 
type, only the preexistent characters are inherited. In the case 
of progressive evolution, characters which are acquired, or added 
to those already existing, are inherited, thus constituting acceler- 
It is a fact of ordinary observation on animals and men, that 
many and apparently most of the structural characteristics of one 
generation are inherited by its offspring. Not only is this the 
case, but the functioning of organs which depend on minute his- 
tological peculiarities is inherited. Such are points of mental 
and muscular idiosyncrasy ; of weakness and strength of all or 
any of the viscera, and consequent tendencies to disease or vigor 
of special organs. Darwin has collected in his work on the De- 
scent of Man, numerous instances of the inheritance of various 
tricks of muscular movement of the face, hands, and other parts 
of the body. 
It is however claimed by Weismann and others, that such char- 
acteristics as are thus inherited are not " acquired " but are " con- 
genital." And they appeal to various experiments on the breed- 
ing of mutilated animals as evidence of the truth of their position. 
It is undoubtedly true that mutilations and injuries are not as a 
general rule inherited. This is also one of the well-known facts 
of ordinary observation. Were this customary, there would 
not be at the present time a sound plant or animal on the earth 
for what individual of either kingdom has not had an ancestor 
mutilated at some or many periods of past times ? But this is a 
proposition widely different from that which the paleontologist is 
called on to contemplate. 
