You are very plucky about Pangenesis, and I much wish that you could have any success. I do not understand your scheme. Do you intend to operate on an ovarium with a single ovule, and to bisect it after being fertilised? I should fear that this was quite hopeless. If you intend to operate on ovaria with many seeds, whether before or after fertilisation, I do not see how you could possibly distinguish any effect from the union of the two ovaria. Any operation before fertilisation would, I presume, quite prevent the act; for very few flowers can be fertilised if the stem is cut and placed in water. Gärtner, however, says, that some Liliaceæ can be fertilised under these circumstances.
If Hooker is correct, he found that cutting off or making a hole into the summit of the ovarium and then inserting pollen caused the fertilisation of the ovules. This has always stretched my belief to the cracking point. I think he has published a notice on this experiment, but forget where, and I think it was on 'Papaver.' Dyer could probably tell you about it. Perhaps your plan is to remove one half of the ovarium of a one-seeded plant and join it on to the ovary of another of a distinct var., with its ovule removed; but this would be a frightfully difficult operation.
I am very sorry to hear about your ill success with cats, and I wish you could get some detailed account of the Belgium trials.
Yours very sincerely,
C. Darwin.
April 16, 1881.
My manuscript on Worms has been sent to printers, so I am going to amuse myself by scribbling to you on a few points; but you must not waste your time in answering at any length this scribble. Firstly, your letter on intelligence was very useful to me, and I tore up and rewrote what I sent you. I have not attempted to define intelligence, but have quoted your remarks on experience, and have shown how far they apply to worms. It seems to me, that they must be said to work with some intelligence, anyhow, they are not guided by a blind instinct.
Secondly, I was greatly interested by the abstract in 'Nature' of your work on Echinoderms; the complexity, with simplicity, and with such curious co-ordination of the nervous system, is marvellous; and you showed me before what splendid gymnastic feats they can perform.
Thirdly, Dr. Roux has sent me a book just published by him, 'Der Kampf der Theile,' &c., 1881 (240 pages in length). He is manifestly a well-read physiologist and pathologist, and from his position a good anatomist. It is full of reasoning, and this in German is very difficult to me, so that I have only skimmed through each page, here and there reading with a little more care. As far as I can imperfectly judge, it is the most important book on evolution which has appeared for some time. I believe that G. H. Lewes hinted at the same fundamental idea, viz. that there is a struggle going on within every organism between the organic molecules, the cells, and the organs. I think that his basis is that every cell which best performs its function is as a consequence at the same time best nourished and best propagates its kind. The book does not touch on mental phenomena, but there is much discussion on rudimentary or atrophied parts, to which subject you formerly attended. Now if you would like to read this book, I will send it after Frank has glanced at it, for I do not think he will have time to read it with care. If you read it and are struck with it (but I may be wholly mistaken about its value), you would do a public service by analysing and criticising it in 'Nature.' Dr. Roux makes, I think, a gigantic oversight in never considering plants; these would simplify the problem for him.
Fourthly, I do not know whether you will discuss in your book on the 'Mind of Animals' any of the more complex and wonderful instincts. It is unsatisfactory work, as there can be no fossilised instincts, and the sole guide is their state in other members of the same order and mere probability. But if you do discuss any (and it will perhaps be expected of you) I should think that you could not select a better case than that of the sand-wasps, which paralyse their prey, as formerly described by Fabre in his wonderful paper in 'Annales des Sciences,' and since amplified in his admirable 'Souvenirs.' Whilst reading this latter book, I speculated a little on the subject. Astonishing nonsense is often spoken of the sand-wasp's knowledge of anatomy. Now will anyone say that the Gauchos on the plains of La Plata have such knowledge, yet I have often seen them prick a struggling and lassoed cow on the ground with unerring skill, which no mere anatomist could imitate. The pointed knife was infallibly driven in between the vertebræ by a single slight thrust. I presume that the art was first discovered by chance, and that each young Gaucho sees exactly how the others do it, and then with a very little practice learning the art. Now I suppose that the sand-wasps originally merely killed their prey by stinging them in many places (see p. 129 of Fabre, 'Souvenirs,' and page 241), on the lower and softer side of the body, and that to sting a certain segment was found by far the most successful method, and was inherited, like the tendency of a bull-dog to pin the nose of a bull, or of a ferret to bite the cerebellum. It would not be a very great step in advance to prick the ganglion of its prey only slightly, and thus to give its larvæ fresh meat instead of old dry meat. Though Fabre insists so strongly on the unvarying character of instinct, yet it shows that there is some variability, as on pp. 176, 177.