84 ROBERT H. BOWEN. 



PLATE II. 



Figs. 27 and 28 are from Murgantia histrionica ; Figs. 15, 16, z\A, 2iB and 

 22 are from Brochymena quadripustnlata ; the others are from Enschistus 

 euschistoides. All the figures are from cells of the large generations. 



FIG. 15. Late stage in the disappearance of the chromophilic substance. 

 (Benda.) 



FIG. .16. Final stage in the disappearance of the chromophilic substance. 

 (Benda.) 



FIG. 17. Early stage in the drawing out of the nebenkern, showing the 

 vacuoles and beaded threads (central substance) which have recently appeared 

 in the chromophobic substance. (Cajal.) 



FIGS. 18, 19. Same as Fig. 17. Fig. 19 is a cross-section of the nebenkern 

 at right angles to the major axis of the spermatid. (Kopsch.) 



FIG. 20. Cross-section of the nebenkern made like Fig. 19, at a stage 

 slightly later than that of Fig. 17. (Cajal.) 



FIG. 21. Cross-sections of the nebenkern made like Fig. 19, approximately 

 at the stage of Fig. 15. A, through the level of the chromophilic plate-work; 

 B, above (or below) the level of the chromophilic plate-work. (Benda.) 



FIG. 22. Cross-section of the nebenkern made like Fig. 19, after the final 

 disappearance of the chromophilic substance. (Benda.) 



FIGS. 23, 24. Intermediate stage in the lateral fusion of the threads of 

 central substance. Fig. 24 is a cross-section of the nebenkern made like Fig. 

 19. (Cajal.) 



FIG. 25. Portion of the mitochondrial sheaths at about the stage of Fig. 

 26. At one end the sheaths were turned upward and so cut in cross-section. 

 (Kopsch.) 



FIG. 26. Final stage in the condensation of the central substance; the 

 threads of Fig. 23 have fused to form a single, axial core for each of the 

 nebenkern halves. (Cajal.) 



FIGS. 27, 28. Development of the bleb-like swellings on the mitochondrial 

 sheaths. Fig. 27 is a small portion of the tail region near the head of the 

 sperm. Fig. 28 is a cross-section of three sperm tails at the stage of Fig. 27. 

 (Benda.) 



