In a letter (#193) to H.P. Lovecraft, March 2, 1932, we learn:

As to my feelings toward the mythical Picts, no doubt you are right in comparing it to the Eastern boy’s Indian-complex, and your own feelings toward Arabic things. My interest in the Picts was always mixed with a bit of fantasy — that is, I never felt the realistic placement with them that I did with the Irish and Highland Scotch. Not that it was the less vivid; but when I came to write of them, it was still through alien eyes — thus in my first Bran Mak Morn story3 — which was rightfully rejected — I told the story through the person of a Gothic mercenary in the Roman army; in a long narrative rhyme which I never completed, and in which I first put Bran on paper, I told it through a Roman centurion on the Wall; in “The Lost Race” the central figure was a Briton; and in “Kings of the Night” it was a Gaelic prince. Only in my last Bran story, “The Worms of the Earth” which Mr. Wright accepted, did I look through Pictish eyes, and speak with a Pictish tongue!

In that story, by the way, I took up anew, Bran’s eternal struggle with Rome. I can hardly think of him in any other connection. Sometimes I think Bran is merely the symbol of my own antagonism toward the empire, an antagonism not nearly so easy to understand as my favoritism for the Picts.

A letter (#222) to Tevis Clyde Smith, circa November 1932, says:

The readers took well to my “Worms of the Earth”1 story, much to my surprize. I didn’t know how they’d like the copulation touch. My heroes grow more bastardly as the years pass.

Annoyed with himself for making some errors in the story, he tells HPL in a letter (#225b) circa December 1932:

Concerning “Worms of the Earth” — I must have been unusually careless when I wrote that, considering the errors — such as “her” for “his”, “him” for “himself”, “loathsome” for “loathing”, etc.. I’m at a loss to say why I spelled Eboracum as Ebbracum. I must investigate the matter. I know I saw it spelled that way, somewhere; it’s not likely I would make such a mistake entirely of my own volition, though I do frequently make errors. Somehow, in my mind, I have a vague idea that it’s connected some way with the Gaelic “Ebroch” — York.

A letter (#259) To H.P. Lovecraft, ca. September or October 1933:

I haven’t heard from the Britishers, and am on the point of writing them a letter. I’m pretty sure they’ll turn my stuff down. I understand that “Worms of the Earth” is to appear in the Not at Night series.

The Not at Night was a series of books published in England, edited by Christine Campbell Thomson. “Worms of the Earth” appeared in Keep on the Light (London: Selwyn & Blount, 1933). “The Black Stone” appeared in Grim Death (1932). The Britishers that Howard refers to is Publisher Denis Archer (see letter #248).