[In a letter to Fox (January 1841) he shows that his "Species work" was still occupying his mind:—
"If you attend at all to Natural History I send you this P.S. as a memento, that I continue to collect all kinds of facts about 'Varieties and Species,' for my some-day work to be so entitled; the smallest contributions thankfully accepted; descriptions of offspring of all crosses between all domestic birds and animals, dogs, cats, etc., etc., very valuable. Don't forget, if your half-bred African cat should die that I should be very much obliged for its carcase sent up in a little hamper for the skeleton; it, or any cross-bred pigeons, fowl, duck, etc., etc., will be more acceptable than the finest haunch of venison, or the finest turtle."
Later in the year (September) he writes to Fox about his health, and also with reference to his plan of moving into the country:—
"I have steadily been gaining ground, and really believe now I shall some day be quite strong. I write daily for a couple of hours on my Coral volume, and