484 JEAN REDMAN OLIVER 



few stages could be found in which the annulus was in the course 

 of its movement. 



After the annujus has reached its final position, about 6.0 n 

 from the nucleus, a striking change takes place in the proximal 

 half of the posterior centrosome. It becomes lengthened in a 

 direction at right angles to the axial filament, at the same time 

 becoming slightly bent, so that it consists of two arms, one 

 continuous with the tail filament, and the other at right angles 

 to it (fig. 30). The po'int of junction of these two arms now 

 thins away, and finally breaks through, leaving the centrosome 

 divided into two usually unequal bodies, lying side by side, in 

 the proximal end of the caudal tube (figs. 31 and 32). This 

 division occurs at about the same time that the staining quality 

 of the nucleus begins to diminish, a change which permits the 

 ready recognition of the anterior centrosome again (fig. 30). It 

 has also elongated in a direction transversal to the axia filament, 

 across the base of the nucleus, and has also divided inlto halves. 

 These two bodies become later attached by thin filaments, each 

 to its corresponding fellow of the posterior centrosome (figs. 34 

 and 35). These filaments are imbedded in a homogeneous hya- 

 line substance, and enclosed externally by the delicate cell mem- 

 brane, all together forming the neck of the adult spermatozoon. 

 The structural weakness at this point accounts for the frequency 

 with which the head is seen broken away from the connecting 

 piece. 



At the completion of the changes outlined in the foregoing the 

 spermatozoon has nearly attained its adult form, save for an 

 irregularly rounded mass of cytoplasm, which is still attached to 

 the connecting piece. The most of the cyptolasm of the sper- 

 matid, however, has broken up into rounded masses which have 

 become detached and lie along the boundary of the lumen of the 

 tubule. The spermatozoon itself now becomes free in the lumen 

 and passes over into the rete testis, and from thence to the 

 epididymis, where the last remnant of the adherent cytoplasm 

 is lost. In this region what may be considered as the mature 

 spermatozoa are to be found. 



