g peculiarities being hereditary, [we
know that some change in the germinal vesicle is effected, which
will only betray itself years after] diseases--man, goitre, gout,
baldness, fatness, size, [longevity <illegible> time of reproduction,
shape of horns, case of old brothers dying of same disease]. And we
know that the germinal vesicle must have been affected, though no
effect is apparent or can be apparent till years afterwards,--no
more apparent than when these peculiarities appear by the exposure
of the full-grown individual. <That is, "the young individual is as
apparently free from the hereditary changes which will appear
later, as the young is actually free from the changes produced by
exposure to certain conditions in adult life."> So that when we see
a variety in cattle, even if the variety be due to act of
reproduction, we cannot feel sure at what period this change became
apparent. It may have been effected during early age of free life
<or> foetal existence, as monsters show. From arguments before used,
and crossing, we may generally suspect in germ; but I repeat it
does not follow, that the change should be apparent till life fully
developed; any more than fatness depending on heredity should be
apparent during early childhood, still less during foetal
existence. In case of horns of cattle, which when inherited must
depend on germinal vesicle, obviously no effect till cattle
full-grown. Practically it would appear that the [hereditary]
peculiarities characterising our domestic races, therefore
resulting from vesicle, do not appear with their full characters
in very early states; thus though two breeds of cows have calves
different, they are not so different,--grey-hound and bull-dog.
And this is what is <to> be expected, for man is indifferent to
characters of young animals and hence would select those full-grown
animals which possessed the desirable characteristics. So that from
mere chance we might expect that some of the characters would be
such only as became fully apparent in mature life. Furthermore we
may suspect it to be a law, that at whatever time a new character
appears, whether from vesicle, or effects of external conditions,
it would appear at corresponding time <see _Origin_, Ed. i. p. 444>.
Thus diseases appearing in old ag