City series

Story, first published: Astounding Science Fiction, Nov. 1944

In ... "Desertion," the stage is set for the disappearance of the human race from the Earth. The scenario is moved off Earth to Jupiter. Attempts to colonize Jupiter have failed consistently. To withstand the dangerous climate, explorers have been changed by a matter converter into Lopers, the indigenous Jovian life-form. Kent Fowler, head of Dome No. 3, Jovian Survey Commission, has sent five men into the howling maelstrom of the giant planet, but none have returned. To solve the mystery, Fowler, accompanied by his aging dog, Towser, decides to find out for himself.
On the surface of Jupiter, Fowler and Towser discover a whole new world of sensations, a whole new sense of being. Their intelligence has been augmented, and they can now communicate telepathically. The mystery of the missing men has been solved - they have deserted the human race for the good life of a Loper. Fowler and his dog cannot resist the temptation to stay, either.

Ewald, Robert J.: When the Fires Burn High and the Wind is from the North, p.42-43