Thanks HBD for his lectures On the germs and vestiges of disease [1861].

Thinks his reasoning that the V. M. F. ("force exhibited in the operations of life") is not a "given quantity" is satisfactory.

How far the conditions of life affect the forms of organic life puzzles CD more than any other part of his subject. Thinks he may have underrated its importance in Origin.

Asks for source of the quotation on regeneration in HBD’s work.

At CD’s request HBD has traced the quotation; it is on regeneration from Charles White in W. B. Carpenter’s Comparative physiology (1854), p. 480.

Is gratified that CD thinks some of the arguments in his book [Lectures on the germs of disease (1861)] are satisfactory.

Thanks for information [on regeneration quotation].

Sends CD a form he has devised of a proper genealogical table of three or four generations of the families of medical cases, so that hereditary transmission may be more accurately and fully recorded.

CD thinks HBD’s tables would be a considerable gain because "the importance of hereditary transmission can hardly be exaggerated from every point of view". Makes suggestions.

Asks him to send any remarkable cases of inheritance to him and, as well, any case of regrowth of amputated additional digit.

Sends copy of the table, which now embodies CD’s suggestions [see 4117].

Gives instances of persons born with two thumbs and comments on hereditary factor.

The [genealogical] table seems excellent. Would be obliged for any further information about the children of the cousins – the case surprises CD.

Suggests man’s original mode of walking and running is similar to that of quadrupeds.

He also suggests CD answer critics who say no new species has ever been unequivocally traced to its origins, by pointing out that there is no unequivocal account of the origin of surnames.

Thanks HBD for his note. The analogy of surnames had not occurred to CD – only that of language generally, as shown so well by Lyell. Fears HBD’s argument about progression would not have much weight.

Asks CD’s opinion of his suggestion that a distinctive mark of species may be the duration of pregnancy, incubation, or germination.

"I should expect that the period of gestation will differ very little in the individuals of the same species, as long as its conditions of life remained the same. But I doubt whether it is sure as an absolute criteria; for although little or nothing on this field can be known with respect to species in a state of nature, yet with races of the same species as with dogs and cattle, the period is known slightly to differ. In the generation of seeds from the same capsule there is often the most wonderful and inexplicable difference in the periods".