irely, from the residue of
undeveloped germs, which, not having been employed in the structure and
work of the individual, have been free to multiply and form the
reproductive elements whence future individuals are derived. Hence the
singular inferiority not infrequently displayed by the children of men
of extraordinary genius, especially where the ancestry has been only of
a mediocre ability. The valuable germs have been used up in the
individual, and rendered sterile in the structure of his person. Hence,
too, the "strong tendency to deterioration in the transmission of every
exceptionally gifted race." Mr. Galton's hypothesis "explains the fact
of certain diseases skipping one or more generations," and it "agrees
singularly well with many classes of fact;" and it is strongly opposed
to the theory of use-inheritance. The elements which are used die almost
universally without germ progeny: the germs which are _not_ used are the
great source of posterity. Hence, when the germs or gemmules which
achieve development are either better or worse than the residue, the
qualities transmitted to offspring will be of an inverse character. If
brain-work attracts, develops _and sterilizes_ the best gemmules, the
ultimate effect of education on the intellect of posterity may differ
from its immediate effect.

EARLY ORIGIN OF THE OVA.

As the ova are formed at as early a period as the rest of the maternal
structure, Galton notices that it seems improbable that they would be
correspondingly affected by subsequent modifications of parental
structure. Of course it is not certain that this is a valid argument. We
know that the paternal half of the reproductive elements does not enter
the ovum till a comparatively late stage in its history, and it is quite
possible that maternal elements or gemmules may also enter the ovum from
without. If reproductive elements were confined to one special part or
organ, we should be unable to explain the reproduction of lost limbs in
salamanders, and the persistent effect of intercrossing on subsequent
issue by the same mother, and the propagation of plants from shoots, or
of the begonia from minute fragments of leaves, or the development of
small pieces of water-worms into complete animals.

MARKED EFFECTS OF USE AND DISUSE ON THE INDIVIDUAL.

These are, to some extent, an argument against the cumulative
inheritance of such effects. When a nerve atrophies from disuse, or a
duct shrivels, or bone