I wonder if Howells and Prime-Stevenson ever met. Howells was at the absolute center of the American literary scene and knew everyone who was anyone, as well as a great number of writers of lesser renown, so it's certainly possible!

In particular, one of Howells' many dear friends was Charles Warren Stoddard, a man who would be forgotten today but for the fact that his South Sea Idyls were VERY gay. And Stoddard spent a lot of his adult life in Europe, so he might well have known EPS...