52 INHERITANCE. Chap. XIV. 



tlieir parent-forms, present conspicuous differences, both in 

 their immature and mature states. Look at the seeds of tho 

 several kinds of peas, beans, maize, which can be propagated 

 truly, and see how they differ in 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 dif- 

 ferent 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 *1k <:•]>. early maturity, including the early develop- 

 ment 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 ; fur 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 pecu- 

 liarity 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 more plainly, because they refer to peculiarities which 

 might have supervened, as far as we can see, earlier or later 



