The foundations of The origin of species : a sketch written in 1842 / edited by Francis Darwin.
- Charles Darwin
- Date:
- 1909
Licence: Public Domain Mark
Credit: The foundations of The origin of species : a sketch written in 1842 / edited by Francis Darwin. Source: Wellcome Collection.
76/94 page 44
![object gained in varying form &c. of foetus (beyond certain adaptations to mother’s womb) and there¬ fore selection will not further act on it, than in giving to its changing tissues a tendency to certain parts afterwards to assume certain forms. Thus there is no power to change the course 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-liound 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 age produce children with d°.,—early maturity,—longevity,—old men, brothers, of same disease—young children of d°. I said men do not select for quality of young,—calf with big bullocks. Silk-worms, peculiarities which, appear in caterpillar state or cocoon state, are transmitted to corre¬ sponding states. The effect of this would be that if some peculiarity was born in a young animal, but never exercised, it might be inherited in young animal; but if exercised that part of structure would be increased and would be inherited in corresponding time of life after such training. I have said that man selects in full-life, so would it be in Nature. In struggle of existence, it matters nothing to a feline animal, whether kitten eminently feline, as long as it sucks. Therefore natural selection would act equally well on character which was fully (developed) only in full age. Selection could tend to alter no character in foetus, (except relation to mother) it would alter less in young state (putting on one side larva condition) but alter every part in full-grown condition. Look to a foetus and its parent, and again after ages foetus and its (i.e. the above mentioned parents) descendant; the parent more variable (?) than foetus, which explains all.](https://iiif.wellcomecollection.org/image/b31351761_0078.jp2/full/800%2C/0/default.jpg)
