he head, instead of a horn, a bony
lump attached merely to the skin. Such cases may seem to prove that
mutilation _associated with morbid action_ is occasionally inherited or
repeated with a promptitude and thoroughness that contrast most
strikingly with the imperceptible nature of the immediate inheritance of
the effects of use and disuse; but they by no means prove that
mutilation in general is inheritable, and they are absolutely no proof
whatever of a _normal_ and non-pathological tendency to the inheritance
of acquired characters. Those who accept Darwin's special explanation
of the supposed inheritance of mutilations, ought to notice that his
explanation applies equally well under a theory which is strongly
adverse to use-inheritance--namely, Galton's idea of the sterilization
and complete "using up" of otherwise reproductive matter in the growth
and maintenance of the personal structure.

Darwin's explanation of inherited mutilations--which, as he notes, occur
"especially or perhaps exclusively" when the injury has been followed by
disease[56]--is that all the representative gemmules which would develop
or repair or reproduce the injured part are attracted to the diseased
surface during the reparative process and are there destroyed by the
morbid action.[57] Hence they cannot reproduce the part in offspring.
This explanation by no means implies that mutilation would _usually_
affect the offspring. On the contrary, in all ordinary cases of
mutilation the purely atavistic elements or gemmules would be set free
from any modifying influence of the non-existent or mutilated part. The
gemmules--as in Galton's theory of heredity and with neuter
insects--might be perfectly independent of pangenesis and the normal
inheritance of acquired characters. Such self-multiplying gemmules
without pangenesis would enable us to understand both the excessive
weakness or non-existence of normal use-inheritance, and the excessive
strength and abruptness of the effect of their partial destruction under
special pathological conditions.

The series of epileptic phenomena that can be excited by tickling a
certain part of the cheek and neck of the adult guinea-pig during the
growth and rejoining of the ends of the severed nerve, are said to be
repeated with striking accuracy of detail in the young who inherit
mutilated toes; but as epilepsy is often due to some _one_ exciting
cause or morbid condition, the single transmission of a highly m