se to where a little brook entered, and I assumed that they
had been brought down by the brook, killed by the sea-water, and cast
on shore. With your skill and great knowledge, I have no doubt that you
will make out much new about the anatomy of worms, whenever you take up
the subject again.

LETTER 551. TO J.H. GILBERT. Down, January, 12th, 1882.

I have been much interested by your letter, for which I thank you
heartily. There was not the least cause for you to apologise for not
having written sooner, for I attributed it to the right cause, i.e. your
hands being full of work.

Your statement about the quantity of nitrogen in the collected castings
is most curious, and much exceeds what I should have expected. In lately
reading one of your and Mr. Lawes' great papers in the "Philosophical
Transactions" (551/1. The first Report on "Agricultural, Botanical,
and Chemical Results of Experiments on the Mixed Herbage of Permanent
Grassland, conducted for many years in succession on the same land," was
published in the "Philosophical Transactions of the Royal Society" in
1880, the second paper appeared in the "Phil. Trans." for 1882, and the
third in the "Phil. Trans." of 1900, Volume 192, page 139.) (the value
and importance of which cannot, in my opinion, be exaggerated) I
was struck with the similarity of your soil with that near here; and
anything observed here would apply to your land. Unfortunately I have
never made deep sections in this neighbourhood, so as to see how deep
the worms burrow, except in one spot, and here there had been left on
the surface of the chalk a little very fine ferruginous sand, probably
of Tertiary age; into this the worms had burrowed to a depth of 55 and
61 inches. I have never seen here red castings on the surface, but it
seems possible (from what I have observed with reddish sand) that much
of the red colour of the underlying clay would be discharged in passing
through the intestinal canal.

Worms usually work near the surface, but I have noticed that at certain
seasons pale-coloured earth is brought up from beneath the outlying
blackish mould on my lawn; but from what depth I cannot say. That some
must be brought up from a depth of four or five or six feet is certain,
as the worms retire to this depth during very dry and very cold weather.
As worms devour greedily raw flesh and dead worms, they could devour
dead larvae, eggs, etc., etc., in the soil, and thus they might locally
add t