We may still need attach (or improved grab), so the paramecium doesn't draw attacks of opportunity when grappling.
Like so?
Attach (Ex): If a giant paramecium hits with a touch attack, it uses its sticky threads to latch onto the opponent’s body. An attached paramecium is effectively grappling its prey. The giant paramecium loses its Dexterity bonus to AC and has an AC of x, but holds on with great tenacity.
An attached giant paramecium can be struck with a weapon or grappled itself. To remove an attached paramecium through grappling, the opponent must achieve a pin against the creature.
Sticky Threads (Ex): The sticky threads covering a giant paramecium hold fast creatures or items that touch it. Giant paramecium have a +8 racial bonus on grapple checks and disarm checks due to their sticky threads.
A weapon that strikes a giant paramecium is stuck fast unless the wielder succeeds on a DC X Reflex save. Prying off a stuck weapon requires a DC X Strength check. The save DC is Constitution-based.
Lantern oil or some other flammable oil (such as alchemist's fire) dissolves the giant paramecium's sticky threads; the creature requires 10 minutes to renew its adhesive coating if doused with oil. A giant paramecium can dissolve its adhesive slime at will, and the substance breaks down 1 minute after the creature dies.
Remove the bits in red?