[11]

Jan 1840

Selection only affects born individuals but their structure in variation depends on fœtus (or eggs/or larvæ) & therefore only such are modified in

[insertion:] we know from diseases, that affections at one time of life are inheritable.

relation to external world = such modifications will act directly to certain extent on fœtuses in regard to size & proportion (as big-bullocked calves) of fœtus with respect to birth & quantity of nutriment &c. Hence fœtuses in early stage or larvæ would change far slower than full-grown animals, although undoubtedly there would be some change possibly only a virtual change, when alteration had gone to great extent by a kind of reflex action or vis medicatrix. Hence we might expect that the fœtuses & young & larvæ (though in less degree, because I conceive larvæ (silk worms!) might be selected allow generic or ordinal

[11v]

affinities & be less useful in specific at least between close species. Hence also we might expect to find traces of parent forms, long since dead, in fœtuses - such being not injurious & being allowed to remain of the same kind as rudimental or abortive structures, but more common & striking. Hence we can understand teeth in whales & parrots bills incomprehensible facts which on ordinary view of species must astound every reflecting mind. Parrots must be less altered descendants of some forms now intermediate between Mammalia? & present birds, than other birds. Hence first class.