44 J- E. WODSEDALEK. 



PLATE VI. 



64 and 65. Two contiguous spermatids, one without chromatin nucleoli, the 

 other with two. The spermatids in general are about equally divided into these 

 two classes. The centrosome is very conspicuous in this stage. 



66. A spermatid showing the large centrosome, surrounded by a clear area, 

 which had emerged from the sphere a short distance away. 



67. A spermatid showing the centrosome in contact with the nuclear wall, 

 and the migration of a portion of the sphere toward the opposite pole. 



68. A spermatid showing the division of the centrosome, the position of the 

 sphere as the acrosome, and the migration of the nucleus toward one side of the cell. 



69. A transforming spermatid showing the separation of the centrosomes and 

 the beginning of the axial filament. Also a dense spherical cytoplasmic body which 

 is likewise present in some of the following stages. 



70. A transforming cell showing a characteristic ring-like structure and position 

 of the posterior centrosome with the axial filament extending through it. 



71. A later stage showing the sloughing off of the posterior ring-shaped centro- 

 some from the axial filament. 



72. A somewhat later stage showing the posterior centrosome completely 

 separated from the axial filament. 



73. A cell showing the cast-off centrosome divided in two. 



74 and 75. Still later stages of the developing spermatozoan showing the char- 

 acteristic position of the posterior centrosome, and the formation of the axial 

 envelope. 



76. A spermatozoan almost fully developed showing the mass of sloughed off 

 cytoplasm including the centrosome. 



77. Side view of a mature spermatozoan showing the arrangement of the chro- 

 matin at the periphery of the head wall. 



78. A mature spermatozoan. 



