Sir

I have the honour to send you the second part of my travel into the inner part of the Tian-shan mountains; I think you have already received the first part, which I left to Mr. Dresser, Tenderden street 6, for sending this book to you.² It contains general observations about the nature, the geological and orographical formation and the nomade inhabitants of these very little known innermost asiatic mountains, and some zoological observations, which may be perhaps of some interest for you. If you would allow me to translate in english a monographical study about the relations between systematic affinities and geographical range of the wild sheep, and the probable influence of struggle for life with the domesticated sheep on some modifications of zoological characters of the different wild species—and if you find this paper worthy to be added as an appendix to a new edition of your “domesticated animals and cultivated plants”— (This book I have read only in a russian translation, not english, and therefore translate again the russian title of it.) that will be an honour of which I dreamed for two years, since that paper is published in russian.³ And now I have a fear that such a suggestion is an indiscreet one. I fear also that this very first attempt of investigating a quite untouched question, and a difficult one will prove weak enough—but its subject is one of high interest and a beginning must be done—may abler men continue—and therefore the protection of your high authority to my essay may be useful for provoking new investigations.

I have also left to Mr. Dresser, for showing you, a sery of central asiatic thrushes, to which he promised to add some instructive chinese specimens from Mr. Swinhoe.⁴ This sery is to illustrate the modification of Turdus mystacinus into Turd. atrogularis, by sexual selection: the males having originally a spotted throat (T. mystacinus), this growing gradually blacker, to complete black   Now the black throated males are the most numerous, their number increasing with each generation; the females in inverse proportion, mostly maintaining the original spotted throat of both sexes—but some females already black throated like the males, though not so completely.

By this hereditary extension of male characters to both sexes this change will appearingly come to a close: the stages of modifications being so.

1. Both sexes alike, spotted throat; Turd. mystacinus; males then changing;

2. A great sexual difference; male alone black throated; females then changing

3. Both sexes alike again, and both changed in the same way from 1), both black throated.

Now is a transition stage between 2 and 3, and very few males of the 1^st stage, perhaps atavistic; and one specimen somewhat intermediate between Turd. mystacinus and the european T. musicus.

The specimens of Mr. Swinhoe illustrate the origin of Turd. fuscatus and T. Naumanni from the same old type.

A paper of me about this will appear in Mr Dresser’s birds of Europe, with a few separate prints, the first of which for your.⁵

I have the honour, Sir, of being with utmost respect | most truly yours | N. Severtzow

Berlin, 25 September.

If you honour me with an answer, please send if so: 6, Tenterden-str., Hanover square—to Mr. H. E. Dresser for N. Severtzov.