How could the transmission of these varied effects to offspring be
accounted for? Is it possible to believe, with Mr. Spencer, that the
effects of use and disuse on the parts of the personal structure are
simultaneously registered in corresponding impressions on the seminal
germs? Must we not feel, with Darwin apparently,[70] that the _only_
intelligible explanation of use-inheritance is the hypothesis of
Pangenesis, according to which each modified cell, or physiological
unit, throws off similarly-modified gemmules or parts of itself, which
ultimately reproduce the change in offspring? If we reject pangenesis,
it becomes difficult to see how use-inheritance can be possible.