size, colour, and shape, whilst the full-grown plants differ but little.
Cabbages, on the other hand, differ greatly in foliage and manner of growth,
but hardly at all in their seeds; and generally it will be found that the
differences between cultivated plants at different periods of growth are not
necessarily closely connected together, for plants may differ much in their
seeds and little when full-grown, and conversely may yield seeds hardly
distinguishable, yet differ much when full-grown. In the several breeds of
poultry, descended from a single species, differences in the eggs and chickens
whilst covered with down, in the plumage at the first and subsequent moults,
as well as in the comb and wattles, are all inherited. With man peculiarities
in the milk and second teeth (of which I have received the details) are
inheritable, and longevity is often transmitted. So again with our improved
breeds of cattle and sheep, early maturity, including the early development of
the teeth, and with certain breeds of fowl the early appearance of secondary
sexual characters, all come under the same head of inheritance at
corresponding periods.

Numerous analogous facts could be given. The silk-moth, perhaps, offers the
best instance; for in the breeds which transmit their characters truly, the
eggs differ in size, colour, and shape: the caterpillars differ, in moulting
three or four times, in colour, even in having a dark-coloured mark like an
eyebrow, and in the loss of certain instincts;--the cocoons differ in size,
shape, and in the colour and quality of the silk; these several differences
being followed by slight or barely distinguishable differences in the mature
moth.

But it may be said that, if in the above cases a new peculiarity is inherited,
it must be at the corresponding stage of development; for an egg or seed can
resemble only an egg or seed, and the horn in a full-grown ox can resemble
only a horn. The following cases show inheritance at corresponding periods