MY DEAR DE CANDOLLE,--You must set me down as a faithless correspondent. Your pleasant letter of April 6, from Paris, has been long upon my table, and I think there is one of older date somewhere below. But all this spring I have been so overworked that I could respond only to the most necessary letters of business, duties of my professorship, of the Garden, and many other things. Well, my lectures are over, and for the ensuing year I may hope for some emendation. I give up the superintendence of the Botanic Garden, which has become a great burden, and I nominally devolve other university work in part upon an assistant, surrendering at the same time a part of my salary, hoping thereby to purchase time. We shall see if it be possible. But I have to begin with a new assistant, who will need training; but will then, I hope, take much off my hands. My youthful assistant of the past two years goes in a week or two to Europe, to study in some German university for a year or two; to Strasburg, I think, unless he first should go to Sweden, and there study Algæ, with Agardh, if he will receive him. He takes a fancy to lower Cryptogamia. His name is Farlow, an honest, good fellow. He will most likely be in Switzerland in the summer; and I shall give him a letter of introduction to you, whom he will wish to know. But take no trouble on his account, except to introduce him to Dr. Müller, from whom, as a working lichenologist, he could learn much. Well, Mrs. Gray and I are going to set out, two weeks hence, for California. We both need the change, and are curious to see the country, having never seen even the Mississippi! The scientific meeting was to have been held there; but there is now a hitch about it. We go, however, at all events, and expect to pass a month in the Yosemite Valley, and elsewhere in the mountain region. I wish you were here to go with us. Hooker was counted on to go with us; but the very bad state of his mother’s (Lady Hooker) health, and the state of affairs at Kew prevent it.... I hope soon to receive your “Mélanges historiques,” which are sure to interest me. If I can I will write you a long letter from California, or Utah, or the Rocky Mountains!--more interesting than this scrawl from yours ever, ASA GRAY. TO JAMES D. DANA. June 22, 1872. MY DEAR DANA,--I fancy you have got hold of a good topic for your handling, and have a promising inquiry before you, in coördinating cephalization and natural selection as operative on the nervous system of animals. I expect you to get something interesting out of it. But every now and then something you write makes me doubt if you quite get hold just right of Darwinian natural selection. What you still say about struggle not applicable to plants makes me think so. Suppose the term be a personification, as, no doubt, strictly it is. One so fond as you are of personification and good general expressions ought not to object to what seems to me a happy term.