I am very much obliged for your photograph, which I am particularly glad to possess, and I send mine in return.
I see you allude to Hilgendorf's statements, which I was sorry to see disputed by some good German observer. Mr. Hyatt, an excellent palaeontologist of the United States, visited the place, and likewise assured me that Hilgendorf was quite mistaken. (268/4. See Letters 252- 7.)
I am grieved to hear that your eyesight still continues bad, but anyhow it has forced your excellent work in your last essay.
May 4th. Here is what Mr. Weir says:--
"In reply to your inquiry of Saturday, I regret that I have little to add to my two communications to the 'Entomological Society Transactions.'
"I repeated the experiments with gaudy caterpillars for years, and always with the same results: not on a single occasion did I find richly coloured, conspicuous larvae eaten by birds. It was more remarkable to observe that the birds paid not the slightest attention to gaudy caterpillars, not even when in motion,--the experiments so thoroughly satisfied my mind that I have now given up making them."
(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.")
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.