More Letters Of Charles Darwin Volume 1 A Record Of His Work In
Chapter 299
(269/1. The late Mr. Lawson Tait wrote to Mr. Darwin (June 2nd, 1875): "I am watching a lot of my mice from whom I removed the tails at birth, and I am coming to the conclusion that the essential use of the tail there is as a recording organ--that is, they record in their memories the corners they turn and the height of the holes they pass through by touching them with their tails." Mr. Darwin was interested in the idea because "some German sneered at Natural Selection and instanced the tails of mice.")
June 11th, 1875.
It has just occurred to me to look at the "Origin of Species" (Edition VI., page 170), and it is certain that Bronn, in the appended chapter to his translation of my book into german, did advance ears and tail of various species of mice as a difficulty opposed to Natural Selection. I answered with respect to ears by alluding to Schobl's curious paper (I forget when published) (269/2. J. Schobl, "Das aussere Ohr der Mause als wichtiges Tastorgan." "Archiv. Mik. Anat." VII., 1871, page 260.) on the hairs of the ears being sensitive and provided with nerves. I presume he made fine sections: if you are accustomed to such histological work, would it not be worth while to examine hairs of tail of mice? At page 189 I quote Henslow (confirmed by Gunther) on Mus messorius (and other species?) using tail as prehensile organ.
Dr. Kane in his account of the second Grinnell Expedition says that the Esquimaux in severe weather carry a fox-tail tied to the neck, which they use as a respirator by holding the tip of the tail between their teeth. (269/3. The fact is stated in Volume II., page 24, of E.K. Kane's "Arctic Explorations: The Second Grinnell Expedition in Search of Sir John Franklin." Philadelphia, 1856.)
He says also that he found a frozen fox curled up with his nose buried in his tail.
N.B. It is just possible that the latter fact is stated by M'Clintock, not by Dr. Kane.
(269/4. The final passage is a postscript by Mr. W.E. Darwin bearing on Mr. Lawson Tait's idea of the respirator function of the fox's tail.)