To H. H. Leng   26 February 1882

Dear Sir

I wish that I c^d. answer your question, but I cannot.¹ The usual cause of the death of worms is a parasitic larva of a Fly, but this c^d. not apply especially to asphalt pavement.² Worms are very susceptible to certain poisons, & coal-tar is poisonous to plants for a quite extraordinary length of time, & it may be so to earth-worms.— I have here an uncovered tennis court, consisting of concrete, & my sons tell me that they have often noticed dead & dying worms on the smooth surface; & this makes the whole case still more perplexing.—

I am glad that my little book has at all interested you & I remain | Dear Sir | Yours faithfully | Ch. Darwin