36 Papers from the Marine Biological Laboratory at Tortugas. 



FIGS. 122, 123, 124. Three spermatids, showing the various shapes and locations of 

 the accessory chromosome. 



FIGS. 125, 126, 127. Successive stages in the metamorphosis of the spermatid to form 

 the spermatozoon; the accessory chromosome shown in form of a central 

 intensely chromatic sphere. These same cells show a polar cap of chro- 

 matic material (this seen only in iron-hematoxylin preparations). The 

 second contains a mass of eliminated chromatin in its cytoplasm and 

 karyosomes in the nucleus. A short, slender chromatic filament has grown 

 out from the centrosome into the cytoplasm. 



FIGS. 128, 129, 130, 131. Successive stages in the later development of the sperma- 

 tozoon. Only one-half contain a chromatin nucleolus (accessory chromo- 

 some). The cytoplasm has elongated into a tail through which extends 

 the slender chromatic filament much enlarged at the nucleo-proximal 

 end to form a middle-piece or neck. 



FIGS. 132, 133, 134, 135. Successive stages in the final development of the sperma- 

 tozoon, showing the progressive disintegration of the chromatin nucleolus 

 (accessory chromosome still U-shaped in figure 133). 



FIG. 136. Mature spermatozoon stained in iron hematoxylin ; showing chromatic archo- 

 plasmic cap, vesicular head (nucleus), chromatic neck, and axial filament 

 with spiral cytoplasmic fin. 



FIG. 137. Mature spermatozoon stained in methyl green (thionin yields similar result) 

 showing an achromatic archoplasmic cap, a chromatic head, and an achro- 

 matic cigar-shaped neck. 



FIGS. 138, 139. Two of the final stages in the formation of a giant spermatozoon. 



