At last: a post, titled regarding paramecia, that actually refers to paramecia.

So we say a paramecium is asexual, not gender-free.
Well, Duh! It's neuter. Paramecium. Hello?

Actually, by understanding is that paramecia can reproduce either asexually (by division) or "sexually", by fusion of the genetic matter of two separate individuals. Furthermore, the choice is not random. A colony of paramecia, left undisturbed, will reproduce by fission, by an individual dividing into two. But if a separate colony -- a separate population -- is introduced, then the mode switches over to fusion, and consistently, the fusing pairing-paramecium will be from opposite colonies; an individual will not fuse with a member of its own colony. In other words, the species appears to express a reproductive preference in favor of genetic diversity.