the other hand, I remember having in former years seen scores
or hundreds of dead worms after heavy rain. (549/1. "After heavy
rain succeeding dry weather, an astonishing number of dead worms may
sometimes be seen lying on the ground. Mr. Galton informs me that on
one occasion (March, 1881), the dead worms averaged one for every
two-and-a-half paces in length on a walk in Hyde Park, four paces in
width" (loc. cit., page 14).) I cannot possibly believe that worms are
drowned in the course of even three or four days' immersion; and I am
inclined to conclude that the death of sickly (probably with parasites)
worms is thus hastened. I will add a few words to what I have said about
these tracks. Occasionally worms suffer from epidemics (of what nature I
know not) and die by the million on the surface of the ground. Your ruby
paper answers capitally, but I suspect that it is only for dimming the
light, and I know not how to illuminate worms by the same intensity of
light, and yet of a colour which permits the actinic rays to pass. I
have tried drawing triangles of damp paper through a small cylindrical
hole, as you suggested, and I can discover no source of error. (549/2.
Triangles of paper were used in experiments to test the intelligence of
worms (loc. cit., page 83).) Nevertheless, I am becoming more doubtful
about the intelligence of worms. The worst job is that they will do
their work in a slovenly manner when kept in pots (549/3. Loc. cit.,
page 75.), and I am beyond measure perplexed to judge how far such
observations are trustworthy.

LETTER 550. TO E. RAY LANKESTER.

(550/1. Mr. Lankester had written October 11th, 1881, to thank Mr.
Darwin for the present of the Earthworm book. He asks whether Darwin
knows of "any experiments on the influence of sea-water on earthworms.
I have assumed that it is fatal to them. But there is a littoral species
(Pontodrilus of Perrier) found at Marseilles." Lankester adds, "It is
a great pleasure and source of pride to me to see my drawing of the
earthworm's alimentary canal figuring in your pages."

Down, October 13th [1881].

I have been much pleased and interested by your note. I never actually
tried sea-water, but I was very fond of angling when a boy, and as I
could not bear to see the worms wriggling on the hook, I dipped them
always first in salt water, and this killed them very quickly. I
remember, though not very distinctly, seeing several earthworms dead on
the beach clo