The midpiece of the mouse sperma tozoon: Its form and development as seen by surface replication

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Abstract
A method is described for making carbon replicas of the surface of fixed spermatozoa and spermatids. In a study of the undulations of the surface of the midpiece, it has been shown that in the mouse spermatozoon the mitochondria are arranged predominantly in two parallel helices—without exception sinistral—totalling about 87 windings around the flagellum. The variability of this number has been calculated. The origin of this arrangement in spermateleosis has been examined in replicas of spermatids, revealing a rather complicated morphogenesis. It seems that, following the migration of the terminal annulus, elongated mitochondria form a single dextral helix around the flagellum; they then divide, making an orderly arrangement of spherical units; finally, each unit elongates, pushes between the contiguous units, and, by end-to end apposition, contributes to the formation of the regular system of two sinistral helices. A detailed account of this transformation is presented. It is suggested that, for tissues of sufficient hardness, the replica technique can usefully complement the cutting of thin sections.