|A human scientist discovers that the Drongheda, a whale-like alien species, do sophisticated mathematics that he can access by climbing inside an orifice and implanting electrodes inside their bodies. The story is told by one member of a team of humans working with that scientist to essentially "mine" the mathematics to be used back on earth. Strangely, the aliens do not seem otherwise intelligent or even sentient. It is unclear whether they even know that the humans are there.
|(quoted from In Alien Flesh)|
But, maybe the Drongheda was evolving, in intelligence, Reginri thought. The things seemed content to swim in the great oceans, spinning crystalline-mathematical puzzles for their own amusement. And for some reason they had responded when Vanleo first jabbed a probing electronic feeler into a neural nexus. The creatures spilled out realms of mathematical art that, Earthward, kept thousands working to decipher it -- to rummage among a tapestry of cold theorems, tangled referents, seeking the quick axioms that lead to new corridors, client pools of geometry and the intricate pyramiding of lines and angles, encasing a jungle of numbers.
Spoiler Alert: If you want to read and be properly surprised by this story, you should stop reading this summary now as some of the unexpected twists (and they are rather twisted twists!) are going to be revealed.
The narrator is recalling his experiences with the Drongheda after he has returned home. His spouse is concerned that he is not behaving like himself and wakes up sweating in the night from troubling dreams. He tells her about how he nearly got trapped inside one of the creatures as its flesh throbbed around him, which does sound nightmare inducing. But, that's not really the problem. It turns out that the mathematics is part of the Drongheda's mating ritual (perhaps evolved as a display like a peacock's tail) and the orifice they had been climbing in was a sex organ. The seemingly-scary experience of being trapped inside the body of a Drongheda was actually some sort of inter-species sexual intercourse. In fact, rather than being afraid of it, the narrator finds that he is actually turned on by it and plans to go back for more! (For this reason, I'm tagging this work with the label "romance". I'm not exactly sure if that is the right word, but I don't currently have a better option.)
This story was originally published in the September 1978 issue of The Magazine of Fantasy and Science Fiction. It has been reprinted many times, most notably in a 1986 Tor anthology of the same name.