(A) Steps of spermatid differentiation: (1) Immature spermatid with round shaped nucleus. The acrosome vesicle is attached to the nucleus, the tail anlage fails contact to the nucleus. (2) The acrosome vesicle is increazed and flattened over the nucleus. The tail contacted the nucleus. (3–8) Acrosome formation, nuclear condensation and development of tail structures take place. The mature spermatid (8) is delivered from the germinal epithelium. Semi-schematic drawing on the basis of electron micrographs. From Ref. . (B) Development of a giant spermatid by confluence of double headed spermatids of a clone. The giant spermatid remains in contact with the Sertoli cell. Drawing on the basis of electron micrographs. From Ref. . (C) Differentiation of acrosomeless spermatozoa. The nuclear condensation and the development of tail structures is not disturbed. The acrosome, however, fails to establish contact to the nucleus of the spermatid and remains in the Sertoli cell cytoplasm. Drawing on the basis of electron micrographs. From Ref. .