My dear Darwin

The word is ‘Hypermetropsy’ in the letter—but ‘Hypermetropia’ is the better & usual word.—¹ In case you have not by you Donders’s book on Ametropia, London 1864² I extract from page 245 as follows:

“The Hypermetropic structure is hereditary: if one of the parents suffers from H. we find the same anomaly usually in one or more of the children; sometimes, too, several brothers & sisters are hypermetropic, without the anomaly being observable in either of the parents.”— This heredity is a matter of constant experience in ophthalmic practice.³ But according to my observations there is the greatest uncertainty & irregularity in the inheritance of this form of Eye— I have several cases of it in 3 & 4 generations— Did I not send you some facts as to this?—⁴ I have not your book⁵ by me at the moment or I w^d. refer.— The fact mentioned by the Dutchman is a very interesting one—but whether it is of Scientific value is another matter— Hypermetropia is very common—rather high degrees of it are not rare— It is very uncommon for all the members of a family to be affected even where it is strongly marked in some individuals—and in the case of two families so long diverged— with such multiple crossings in course of the two lines of descent, it is hard to conceive that the coincidence of Hypermetropia in the two contemporary families at the present time implies any reliable proof of common inheritance though no doubt the fact may be so & there may be the causative connexion.

yrs most truly | W. Bowman

Suppose you refer to Donders.⁶ He may I may almost say must have personal knowledge of these families—