Sir!

Your kindness has forwarded me with two workes of such interest and importance (Monograph of the Cirripedia¹ and Origin of species), that I was nearly ashamed to offer you the small contribution to the biology of lower animals, which now you will have already received, at least I ordered my librarian, Engelmann, some weeks ago, to send you in my name my last publication (Beiträge zur Parthenogenesis der Arthropoden).² I hope my researches on parthenogenesis will show you, that this mode of propagation has ceased to be a mere curiosity, but has a peculiar signification and will best, I think, be considered as a case of atavisme.

The pseudova, this is sure, cannot be distinguished from the ova.³ Now nobody till now wondered about their development without interference of the male element. Ova, they said, are only capable of developement after having been fertilised.— In the successive generations of organic beings at first animals might have been found, that were propagated by pseudova, then, when the capacity of the animals to produce pseudova was no more sufficient for a sound development, a fertilisation was needed and afforded by the union of the two sexes in one being—the hermaprodit. Later these hermaphrodits were by and by separated into females and males, and these again by atavisme (inheritance from their first ancestors) became the faculty to produce ova (“pseudova”) which were developed without having been fertilised.

If in the beginning of my researches I had called pseudova all those eggs, which without having been fertilised are able of development, my adversaries—in England at least—would have been contented.

For your photograph, which I got through our common friend Lewes,⁴ my best thanks. I send mine in return⁵ and cannot conclude my letter without giving expression to my deep veneration and admiration for you, to whom we owe that actually the investigation of organic life has taken this new and for science so extraordinary useful direction.

I am, Sir, your most obedient | servant | Charles de Siebold