up in the "Genera Plantarum." I heartily wish you safe through your
work,...

LETTER 756. TO F.M. BALFOUR. Down, September 4th, 1880.

I hope that you will not think me a great bore, but I have this minute
finished reading your address at the British Association; and it has
interested me so much that I cannot resist thanking you heartily for the
pleasure derived from it, not to mention the honour which you have done
me. (756/1. Presidential address delivered by Prof. F.M. Balfour before
the Biological Section at the British Association meeting at Swansea
(1880).) The recent progress of embryology is indeed splendid. I have
been very stupid not to have hitherto read your book, but I have had of
late no spare time; I have now ordered it, and your address will make
it the more interesting to read, though I fear that my want of knowledge
will make parts unintelligible to me. (756/2. "A Treatise on Comparative
Embryology," 2 volumes. London, 1880.) In my recent work on plants I
have been astonished to find to how many very different stimuli the
same small part--viz., the tip of the radicle--is sensitive, and has
the power of transmitting some influence to the adjoining part of
the radicle, exciting it to bend to or from the source of irritation
according to the needs of the plant (756/3. See Letter 757.); and all
this takes place without any nervous system! I think that such facts
should be kept in mind when speculating on the genesis of the nervous
system. I always feel a malicious pleasure when a priori conclusions are
knocked on the head: and therefore I felt somewhat like a devil when I
read your remarks on Herbert Spencer (756/4. Prof. Balfour discussed
Mr. Herbert Spencer's views on the genesis of the nervous system, and
expressed the opinion that his hypothesis was not borne out by recent
discoveries. "The discovery that nerves have been developed from
processes of epithelial cells gives a very different conception of their
genesis to that of Herbert Spencer, which makes them originate from
the passage of nervous impulses through a track of mingled colloids..."
(loc. cit., page 644.))...Our recent visit to Cambridge was a brilliant
success to us all, and will ever be remembered by me with much pleasure.

LETTER 757. TO JAMES PAGET.

(757/1. During the closing years of his life, Darwin began to
experimentise on the possibility of producing galls artificially. A
letter to Sir J.D. Hooker (November 3rd, 1880) show