Opopaea apicalis

SPERM TRANSFER FORM (fig. 25): Large sperm transfer forms (.25 Mm),

composed of only a chromatin thread that is embedded in an electron-dense matrix and surrounded by a thin (, 70 nm) homogeneous secretion sheath (fig. 25A, B).

Spermatozoa (fig. 25): Acrosomal complex: AV absent. AF absent. Nucleus: prcN condensed chromatin thread that is tightly screwed (fig. 25C). peN absent. NC inapplicable (due to missing AF). Axoneme: absent.

NOTES ON SPERMIOGENESIS (fig. 25): The chromatin is highly condensed and appears threadlike (fig. 25 C–E). Moreover, the chromatin thread is helically contorted. Some

mitochondria are visible. At the end of spermiogenesis, the manchette of microtubules, which surround the developing nucleus (fig. 25E), disintegrates.