Sir!

I have read the paper from You: “on the origin of species, etc.” with great pleasure and greater information.¹ But a law, very important by inheritance, i have not found asserted, the law, that to young animals are inherited in the utmost strength those organs, which will be utmost used and exercised by the father and the mother before the conception of the young animal and by the mother when pregnant with it.²

By this cause a young hunting dog, for example, is inherited with a finer nose, when the father before his uniting with the mother or when the pregnant mother were frequently used by hunting, and a colt is inherited with stronger muscles, when the father and the mother before their uniting or when the pregnant mother were frequently used by riding or carrying.

This law proves the frequently inheritance even of conditions no endurings for life-time, and it seems to be a cause, quickly to spread conditions, founded upon surprising development; and by this means efficiently to favour the origin of new varieties, species, genera and families.

I hope, You will be pleased to excuse me, for not better knowing the english language.

I am respectfully | Dr. Heine, | physician.

Bitterfeld (near Leipsic)

the 10 of Mars 1865.

To Mr. Charles Darwin. | author of the book: on the origin of species, etc.