[17]

Feb / 41/

When we reflect on what I believe is case that man by art (select & var) can make organisms, different & hereditary at any period of life up to cessation of reproduction (thus peas, beans cotton? Silk coccoon wheat at L early period of seed - silk-worms diseases at particular ages, (though latter probably, consequences of earlier changes - diseases of heart Dr. Holland's case come on after reproductive system is getting old) one is led to conclude that variation, which may be hereditary, takes place at all periods of life (agrees with the small changes known in grafted trees &c &c during individual life) and that every change is not necessarily effect of some change on conditions in embryo - the embryo itself not necessarily affected, excepting that its future growth at different periods is to vary. Should this be so, as selection does not act on young state, the variations with tendency to be hereditary, at that age must be counteracted by crossing but not so with such variation in older age, for here selection acts. Hence young or fœtuses, in wild species will generally agree closer than old form. Compare early puppy of Bull-dog & Greyhound

[insertion:] I was led to this thought by hearing bill of young, cross-beak not crossed.

Possibly variation which has supervened when sex is fully developed, may go with sex & so accounts for secondary male characters.

[in margin:] Compare Lettuce Cabbage seeds

[in margin:] teeth of grown people or second set, being hereditary a case of changes effect of antecedents

[over]

[17v]

variations having tendency to come on at different periods in two varieties what confusion by their crossing.

Possibly where part entirely left out, or where whole form affected, the fœtus in early stage is affected.

If seeds be alike as in cases, when not selected & differ when selected &c & it wd prove that parts that corresponding parts vary & are hereditary without other part necessarily varying & as different parts appear at different ages, necessarily there will be corresponding variation at corresponding ages.

Best case to show corresponding variation at corresponding ages, must be in a part not appearing first at late age

L Sweet Peas Lathyrus are there many varieties - seeds similar? greatly diverse in Pisum -Think of any other leguminous plant with many races where seed not object - Kidney Beans??