I thank you also for the good spirit in which you take, as I meant them, my criticisms upon your article on Species, etc. There is no progress to be made upon such interesting subjects without free criticism, because without it we cannot perfectly clear up our own views nor impart them perfectly to others. And especially, since I have so often to criticise the views or writings of persons for whom I have no particular regard, it is pleasant, if only for the sake of impartiality, to criticise those for whom you have the greatest regard and respect. So I particularly like it when I can criticise such a near friend as J. D. Hooker or Bentham, and I believe they like it, too, at least Hooker, who is himself a very free critic. Of course, I know very well that you will be likely to turn all the points I made. The question upon which of the two foundations the idea of species rests, I well know is not to be settled off-hand by any bit of argument. Pray take up the cudgels against me whenever an occasion offers. As to theoretical views, you and I receive and use them as means, not as ends, and expect to change many of them from time to time. Such especially as relate to origins and causes are the questions which we ask, rather than answers that we receive; and we put our questions variously according to the leadings of the case at the time. But this is all commonplace and trite. It is curious to see that Owen, in his Aye-aye paper, has come to adopt Heer’s[58] views essentially, of course without the slightest allusion to Heer. Our civil war goes on slowly, but very surely, toward the destruction of negro slavery; and with all its great cost, we may hope for future benefit in proportion. By the time we have nearly ended our war, it may be that Europe will have its turn again. I hope not. A. GRAY. TO JAMES D. DANA. CAMBRIDGE, January 20, [1864]. MY DEAR DANA,--Perhaps you may not know, and I hope you may be as pleased as I was to know, that your article of last summer on Geological Periods is reprinted in full in the “Reader” (of London), with an appreciative prefix. Cephalization goes on bravely in your very taking article which you have just sent me. I am much struck with it. In one thing you zoölogists miss it, I think,--in following French customs in dropping the Latin, the vernacular of science, in names. I wish you would write Aphaniptera, etc., which is just as much English after all as Aphanipters, and good for all languages. Have Englishified contractions for all such names if you will; it is well. But in proposing and formally writing of such divisions, etc., pray use the scientific form. The other course has greatly jargonified zoölogy. In botany we have always been more dignified. Moreover I detest “larve,” though Kirby tried to introduce the word. “Larva” has got to be as English as “phenomenon.” But I dare say most would agree with you. I like the ring of most of the new technical terms you have coined....