SOIL ACIDITY AND THE ABSENCE OF EARTHWORMS ON FOXHALL HEATH. I WAS measuring the slope of the land with an improvised waterlevel and my father was helping me to plant posts for " sighting," when I noticed the entire absence of earthworms in the soil. Knowing that the digestive tract of Lumbricus terrestris and Allolobophora longus have calciferous glands which I had noted previously in dissection, I tested the soil reaction in the habitats of Calluna vulgaris and Pteridium aquilinum, and found the reaction in both instances was acid. The soil of Foxhall Heath has a high hydrogen-ion concentration, probably owing to leaching. The calciferous glands of the earthworm, the function of which is probably to neutralize the acids in the half-digested leaves, require calcium carbonate (alkaline). Does this mean that worms can only exist in an alkaline soil ? Although earthworms appeared to be absent on the Heath, I found both terrestrial and freshwater snails near the Mill River which drains the Heath. On the slopes near the Reed Swamp I found a hoard of broken shells, Helix nemoralis, probably the remains of a bird's dinner. In the Mill River the snails were of the genus Planorbis, whose shells are composed of calcium carbonate. The river water gave a near neutral or alkaline reaction necessary for the snail. Here we had an apparent contradiction—the earthworm with calciferous glands unable to exist in acid soil, and the snail which needs calcium for its shell living in the river which drains that soil. The soil is sandy and very porous. I supposed that the calcium salts might have been leached from the upper part of the heath and been washed into the river. Although Sphagnum cymbifolium which is an acidicole is found along part of the river, it grows in a stagnant backwater and not in the open part where Planorbis was found. I wrote to Miss Blackwell of the Royal Holloway College and asked her whether my hypothesis was possible—that the extreme acidity of the peat and the near-neutral reaction of the river water accounted for the absence of earthworms in the peat and the presence of snails in the river. I was unaware then that any work had been carried out on this subiect, but later Professor Salisbury lent me his paper on " The Influence of Earthworms on Soil Reaction and the Stratification of Undisturbed Soils " and this confirmed my independent discovery. Dr. Salisbury also informed me of experiments with Allolobophora foeiida performed by S. H. Hurwitz, " The Reaction of Earthworms to Acids" (Proc. Amer. Acad. Vol. XLVI, pp. 67-81, 1910), and of experiments of Arrhenius with Perichoeta indica and Lumbricus terrestris in which soils were rendered artificially acid OR
ALKALINE
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ADA
E.
M.
QUANTRILL.