This is an actual old-fashioned stethoscope design. More common is open on both ends, like a Pinard Horn, but some of them have the drum head and that probably works better for the slime.
My brain fried when trying to process slime culture where speaking to another dissolves the self while telling each other EVERYTHING and ultimately generating a new, singular consciousness that can also be split into two parallel existences that will individually gather knowledge and experiences... DAFUQ?!
The bigger they are the smarter they are. So it's just like the brain, or more like, more surface there are in a brain, more intelligent or functional the creature is going to be. So, Knowing Water aka Slime is literally liquid brain.
Slime (additional notes)
[ul]~ Can split itself into several separate parts[/ul]
[ul]~ Can reabsorb parts once separate from itself[/ul]
[ul]~ Has immunity to identity crises ***
[/ul]