You searched for: “phorozoa
phorozoon (s) (noun), phorozoons; phorozoa (pl)
A zooid that attaches itself to the back of its parent: While being fixated to its progenitor, the phorozoon carries and nourishes another type at the same time which is called the "gonozooid" that subsequently breaks free to reproduce sexually.

The nonsexual phase or generation of a phorozoon involves an alternation of generations or sequence of reproductive modes.