pes, both constant, it is evident that these cannot both be modified
in the same way as the parent is modified. Many parental modifications
of structure and habit are certainly not conveyed to neuter ants and
bees; other modifications, which are not seen in the parents, being
conveyed instead. Many other circumstances tend to show that the
individual and the transmissible type are independent of each other so
far as modifications of parts are concerned.

It may seem natural to expect the transmission of an enlarged muscle or
a cultivated brain, but, on the other hand, why should it be
unreasonable to expect that a modification which was non-congenital in
origin should still remain non-congenital? Why should the
non-transmission of that which was not transmitted be surprising?

Mr. Spencer thinks that the non-transmission of acquired modifications
is incongruous with the great fact of atavism. But the great law of the
inheritance of that which is a development of the transmissible type
does not necessarily imply the inheritance of modifications acquired by
the individual. Because English children may inherit blue eyes and
flaxen hair from their Anglo-Saxon ancestors, it by no means follows
that an Englishman must inherit his father's sunburnt complexion or
smooth-shaven face. Of course atavism ultimately adopts many instances
of revolt against its sway. But to assume that these changes of type
_follow_ the personal change rather than cause it, is to assume the
whole question at issue. That like begets like is true as a broad
principle, but it has many exceptions, and the non-heredity of acquired
characters may be one of them.

FOOTNOTES:

[2] _Principles of Biology_, Sec. 166, footnote. The English jaws are
somewhat lighter than the Australian jaws, though I could not undertake
to affirm that they are really shorter and smaller. In the typical
skulls depicted on p. 68 of the official guide to the mammalian
galleries at South Kensington, the typical Caucasian jaw is very much
larger than the Tasmanian jaw, although the repulsively obtrusive teeth
of the latter convey the contrary idea to the imagination. Mr. Spencer's
assumption that the ancient Britons had large jaws appears to me
erroneous. (See Professor Rolleston's _Scientific Papers and Addresses_,
i. p. 250.)

[3] Romanes, Galton, and Weismann have made great use of this principle
in explaining the diminution of disused organs. Weismann has given it
the name