Men, Martians, and MachinesMen, Martians, and Machines, a collection of four stories by Eric Frank Russell first published in 1955. Any of these coversthese covers look familiar?
"Mechanistria""Mechanistria", first published in Astounding Science-Fiction, January 1942Astounding Science-Fiction, January 1942, available at the Internet Archive.
"Symbiotica""Symbiotica", also the answer to this question; first published in Astounding Science-Fiction, October 1943Astounding Science-Fiction, October 1943, available at the Internet Archive.
The other two stories in the collection are "Jay Score""Jay Score", first published in Astounding Science-Fiction, May 1941Astounding Science-Fiction, May 1941, available at the Internet Archive, and "Mesmerica""Mesmerica", first published in this collection.