Down, April 16, 1881.
My dear Romanes,
My MS. on 'Worms' has been sent to the 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 tor up and re-wrote what I sent to 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 ("On the locomotor system of Echinoderms," by G.J. Romanes and J. Cossar Ewart. 'Philosophical Transactions,' 1881, page 829.), 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,' etc., 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, in 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 would sent it...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 the '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 any one say that the Gauchos on the plains of La Plata have such knowledge, yet I have often seen them pith 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 vertebrae 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 learns the art. Now I suppose that the sand wasps originally merely killed their prey by stinging them in many places (see page 129 of Fabre's 'Souvenirs,' and page 241) on the lower and softest 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 bulldog 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 larvae fresh meat instead of old dried meat. Though Fabre insists so strongly on the unvarying character of instinct, yet it is shown that there is some variability, as at pages 176, 177. I fear that I shall have utterly wearied you with my scribbling and bad handwriting.
My dear Romanes, yours, very sincerely,