Chapter 297

I write to-day so that there shall be no delay this time in thanking you for your interesting and long letter received this morning. I am sure that you will excuse brevity when I tell you that I am half-killing myself in trying to get a book ready for the press. (267/1. The MS. of "Insectivorous Plants" was got ready for press in March, 1875. Darwin seems to have been more than usually oppressed by the work.) I quite agree with what you say about advantages of various degrees of importance being co-selected (267/2. Mr. Chauncey Wright wrote (February 24th, 1875): "The inquiry as to which of several real uses is the one through which Natural Selection has acted...has for several years seemed to me a somewhat less important question than it seemed formerly, and still appears to most thinkers on the subject...The uses of the rattling of the rattlesnake as a protection by warning its enemies and as a sexual call are not rival uses; neither are the high-reaching and the far-seeing uses of the giraffe's neck 'rivals.'"), and aided by the effects of use, etc. The subject seems to me well worth further development. I do not think I have anywhere noticed the use of the eyebrows, but have long known that they protected the eyes from sweat. During the voyage of the "Beagle" one of the men ascended a lofty hill during a very hot day. He had small eyebrows, and his eyes became fearfully inflamed from the sweat running into them. The Portuguese inhabitants were familiar with this evil. I think you allude to the transverse furrows on the forehead as a protection against sweat; but remember that these incessantly appear on the foreheads of baboons.

P.S.--I have been greatly pleased by the notices in the "Nation."