Just found this blog entry for
The Shadow Over Innsmouth, where it is claimed that the ending was possibly influenced by Kuttner. I've yet to read this story so I cant say.
Variety SF: H P Lovecraft - "The Shadow Over Innsmouth" (novella, free): Intelligent sea-based amphibians have been interbreeding with humanity!
No, the ending was not influenced by Kuttner, who wasn't even publishing at the time the story was written (late 1931). On the other hand, Kuttner was influenced by HPL (as he was by Robert E. Howard and others); in fact in his early career, he was an inveterate mimic, until he began to find his own voice and then the combined voice with his wife -- another member of the Lovecraft Circle with Kuttner -- C. L. Moore); his tales in the Lovecraft vein were collected together in the Chaosium volume The Book of Iod.
Lovecraft had a brief correspondence with Kuttner the final year of HPL's life, giving the young, emerging writer critiques and encouragement, as well as numerous pointers on the benefits of accurate research and the like; his letters to Kuttner were published by Necronomicon Press in 1991.
"The Shadow Over Innsmouth" was originally rejected by
Weird Tales editor Farnsworth Wright as well as others, and lay unpublished for some time before being released as a very small print run by an amateur publisher correspondent of Lovecraft's, William J. Crawford, in 1936, through his Visionary Publishing Company. The first professional publication of the tale was in the first Arkham House title,
The Outsider and Others (1939).
By the time Kuttner was publishing, Lovecraft's fictional career was essentially over... Kuttner began publishing, as I recall, in 1936, and Lovecraft's last original tale was "The Haunter of the Dark" (1935); all that remained of his fictional output were a small handful of revisions or collaborations, such as the (admittedly brilliant) "The Night Ocean" (largely written by Robert H. Barlow) and "In the Walls of Eryx" (a science fiction horror tale) with Kenneth J. Sterling....
The following offers a very brief (but essentially accurate) account of the history of the tale:
The Shadow Over Innsmouth - Wikipedia, the free encyclopedia