334 bulletin: museum of comparative zoology. 



The triple specimen (Fig. 104) is in a slightly more advanced stage. 

 The nucleus, in about the same phase as the one last described, is in this 

 case nearly spherical. The remnants of the iuterzonal filaments have 

 entirely disappeared, but no acrosome is yet visible. The archoplasmic 

 organ, lying in the same position with reference to nucleus and centro- 

 somes as in the double cell, is here clearly differentiated into three 

 deeply staining centres (Fig. 104), which are not, however, separate 

 masses. There are thi*ee centrosomes, minute granules lying at the 

 periphery of the cell, about 10° apart, one opposite each of the archo- 

 plasmic centres. From each centrosome arises a distinct tail filament, 

 all these being more or less twisted together, as is commonly the case. 

 I have not been able to trace any forward extension of the axial filament 

 in connection with the two lateral centrosomes, but from the middle one 

 such a structure is clearly visible, extending inward to the nuclear mem- 

 brane. At its point of junction with the membrane there is a deeply 

 staining knob, no doubt to be regarded as having resulted from the 

 division of the middle centrosome into proximal and distal parts. 

 Apparently, however, the two lateral centrosomes have not yet divided. 

 The nucleus is considerably larger than in the double spermatid (Fig. 

 103), measuring 4 p. in diameter. 



The giant spermatids, whether double, triple, or quadruple, agree with 

 normal cells in the nature of their later metamorphoses, and differ 

 from one another only in size and the number of their tail filaments 

 and centrosomes. The nucleus becomes homogeneous, stains deeply, 

 and assumes the typical conical form ; a spherical acrosome of archo- 

 plasmic nature develops at the slightly truncate apex of the nucleus, 

 the cytoplasm, previously finely reticulate, becomes vacuolate in the 

 neighborhood of the nucleus, which finally comes to lie in a clear area 

 (Figs. 105 and 106). The archoplasmic mass increases in density and 

 bulk, and shows the separation into well-marked spherical masses char- 

 acteristic of the normal spermatozoon (compare Fig. 102 with Fig. 106). 

 There now occur other changes which point strongly toward degenera- 

 tion as the ultimate fate of these giant spermatozoa. Clear vacuoles 

 (Fig. 106) appear in the dark substance of the nucleus ; the cytoplasm 

 is often ragged and torn; the tail filaments appear to fuse (Fig. 105), 

 and then dwindle (Fig. 106) ; and the centrosomes become less sharply 

 defined, as though being gradually diffused. Finally, in many cases all 

 organs of the cell — cytoplasm, middle piece, etc. — are broken down, 

 the nucleus and acrosome alone being recognizable. In certain prepara- 

 tions manv of these isolated nuclei are to be seen. There is, then, 



