Blastophore

It does not, however, happen that the whole spermatosphere is converted into spermatoblasts; there remains a passive portion, which in the earthworm occupies a central position; this is the "sperm-blasophore," or "blastophoral cell."

Associted with the formation of the male sex cells from the time they leave the testes until the spermatozoön becomes fully grown there is a protoplasmic structure, termed the blastophore (Bloomfield, '80, Calkins, '95) in Lumbricus, and the cytophore (Voigt, '85) in Branchiobdella varians.

The cytophore now splits internally in such a way as to separate an inner sphere (blastophore) from an outer envelope.