Fio. 2. Nine stages in the transformation of a spermatid into a spermatozoon. 

 (After Duesberg.) 



A, spennatid with two centrioles, the proximal and the distal, at one side of nucleus and the idio- 

 sonie at the other side. B, stage in which the distal centriole is giving rise to a filament, and in 

 which the idiosome is applied to one side of the nucleus. C, stage in which the nucleus is beginning 

 to emerge from the cytoplasm dragging after it the centrioles ; the filament, now grown longer, is im- 

 mersed in the cytoplasm, the ruffle has appeared, and the idiosome has become the acrosome. D, stage 

 in which the nucleus has begun to become sickle-shaped. E, stage in which the distal centriole has 

 divided into two and the outer one has become a ring. F, stage in which the ring is moving outwards 

 along the filament. G, stage in which the ring has moved beyond the cytoplasm. H, I, two stages in 

 casting off the cytoplasm, ac, Acrosome ; c, proximal centriole ; el, distal centriole ; id, idiosome ; in, 

 ruffle (manchette) ; r, ring centriole. 



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