SPERMIOGENESIS OF THE PRIBILOF FUR SEAL 493 



ABBREVIATIONS 



a., acrosome — h.c, head cap 



u.f., axial filament h.n., nucleus of spermatozoon 



an., annulus m.p., main piece of adult spermatozoon 



c, centrioles n., neck of adult spermatozoon 



c.p., connecting piece n.a., anterior nodules (centrioles) 



c.r., cytoplasm remnant n.p., posterior nodules (centrioles) 



c.t., caudal tube p.c, posterior centrioles. 



d.c, distal centriole r., rodlet 



e.p., end piece of adult spermatozoon s., idiosome, or sphere 



/., caudal tube filaments S.c, cytoplasm of Sertoli cell 



/)., hyaline portion of idiosome s.r., idiosome remnant 



All figures are reproduced at a magnification of one thousand diameters. 



Figs. 1 to 15 First period of spermiogenesis 



Fig. 1 Spermatid shortly after last division of spermatocyte, the idiosome 

 homogeneous, a pair of centrioles (?), c, lying in the cytoplasm below the nucleus. 



Fig. 2 Spermatid showing two deeply staining granules in the idiosome . 



Fig. 3 Spermatid with idiosome containing a single large central body, the 

 acrosome anlage. 



Fig. 4 Spermatid with idiosome separating into the sphere remnant, s.r., and 

 a hyaline portion, h., containing the dense central body, the acrosome. 



Fig. 5 The idiosome begins to flatten against the nuclear wall, which is also 

 slightly flattened. The acrosome is in contact with the nuclear wall and has 

 fused with it. 



Fig. 6 Continuation of flattening of idiosome and acrosome against nuclear 

 wall. The chromatin of the nucleus is becoming more finely divided. 



Fig. 7 The pressure of the idiosome against the nuclear wall has apparently 

 produced an inbending of the latter. In the cytoplasm at the right of the sphere 

 remnant is a large deeply staining body. 



Fig. 8 The idiosome is extending backward around the anterior portion of the 

 nucleus in a cap-like form. The acrosome is also much flattened along the nuclear 

 membrane.. 



Fig. 9 A differentiation has appeared in the substance of the idiosome, or 

 head cap, its outer anterior portion becoming much more dense, a narrow hyaline 

 portion still intervening between this and the nucleus. 



Fig. 10 Spermatid with block-like masses of chromatin in the nucleus. The 

 idiosome is not shown in the section. At the lower boundary the centrioles are 

 seen, with the axial filament extending from the distal one out freely into the 

 lumen of the tubule. 



Fig. 11 The head cap substance has become equally dense throughout. The 

 acrosome has extended along the surface of the nuclear wall below the head cap, 

 and has fused indistinguishably with it, appearing now as a thickened line co- 

 extensive with the under surface of the head cap. The centrioles have migrated 

 inward toward the nucleus, with which the pro.ximal one is now in contact. From 



