EXPLANATION OF FIGURES. 



All figures were outlined with a Zeiss camera lucida, at the level of the stage 

 of the microscope. Zeiss apochromatic immersion 2 mm., ocular 12. Artificial 

 light (gas). 



PLATE 1. 

 Fixation, Benda; stain, Benda. 



FIG. 1. A Sertoli-cell. The three big granules in the basal part, near the nucleus, are fat-droplets. 



Fio. 2. Resting spermatogonium. 



FIG. 3. Dividing spermatogonium, metaphase. 



FIG. 4. First spermatocyte, pachyten stadium 



FIG. 5. First spermatocyte in the second phase of the growth-period. 



FIG. 6. Dividing first spermatocyte, metaphase. The small granules to the right of the spindle and below the equator 



are fat-droplets. 



FIGS. 7, 8, 9. First period of sperm iogenesis. 



FIG. 7. Young spermatid. The granules in the upper left corner are fat-droplets. 

 FIG. 8. More advanced stage. 



FIG. 9. More advanced stage. Note the small acrosome on anterior part of the nucleus. 

 FIGS. 10, 11, 12. Second period of spermiogenesis. 



FIG. 10. The head has assiuned the form of an egg-shaped body, whose long axis is perpendicular to the axial filament. 

 Flo. 11. The head begins to assume its definite form. First indication of disjointing of headcap. Note an idiozomic 

 , remnant near the opening of the caudal tube, on the left. 



FIG. 12. Further stage of the disjointing of the headcap. Idiozomic remnant near the opening of the caudal tube. 



In the upper left corner, first appearance of "tingierbare Korner." Note the sheath developing around 



the axial filament in the future main piece. 

 FIGS. 13, 14, 15,a and b. Third period of spermiogenesis. 



FIG. 13. Migration of the ring. The granule right below the ring is a mitochondrium, not a ccntriole. In the proto- 

 plasmic lobe, remnant of the idiozome (to the right of the ring), mitochondria and "tingierbare Korner," 



darkly stained and fused together. 

 FIG. 14. Deposit of mitochondria on the axial filament in the middle piece. "Tingierbare Korner" to the right 



of the main piece. 

 Flo. 15a. Elimination of protoplasm with some mitochondria, idiozomic remnants (?) and "tingierbare Korner" 



covering part of the head and the anterior part of the middle piece. 

 FIG. 156. Transverse section through the region of the middle piece showing the peripheric disposition of the chon- 



driosomes which are going to be eliminated. To the right, cross-section of the middle-piece; to the 



left and somewhat below, "tingierbare Korner;" in the lower right corner, idiozomic remnants (?). 

 Fio. 16. Fourth period. The spiral filament is formed. Between the spermatozoa, expelled into the lumen, and 



the seminal epithelium, a layer of residual bodies with big granules and vacuoles. 



PLATE 2. 



FIGS. 17-24. Fixation, Regaud; stain, acid fuchsin-methyl green. 



FIG. 17. Spermatid in a stage somewhat more advanced than the cell represented in figure 8. Note the difference 

 in size after the action of two different reagents. 



FIGS. 18-21. Third period of spermiogenesis. Successive stages of the deposit of chondriosomes on the middle piece 

 and the elimination of the residual body, with some chondriosomes. 



FIGS. 22-24. Fourth period of spermiogenesis. Successive stages of the formation of the spirale. 



FIG. 25. From a smear of sperm from the epididymis. Fixation vapors of osmic acid. Stain, Benda. Copulating 

 spermatozoa. 



FIGS. 26-34. From preparations after Cajal and handled further as described in the text. Counterstain: methyl- 

 green for figures 26-30, 33 and 34; Ehrlich's hematoxylin for figures 31 and 32. 



FIG. 26. Spermatogonium with impregnation of mitochondria (?) and of the intracellar apparatus. 



FIG. 27. Two first spermatocytes in the first phase of the growth-period. To the left a perpendicular section, to 

 the right a tangential section. 



FIG. 28. First spermatocyte, second phase of the growth-period. 



FIG. 29. First division, metaphase. 



FIG. 30. First division, anaphase. 



FIG. 31. Second spermatocyte, with two apparatuses. 



FIG. 32. Spermatid in a stage of development corresponding approximately to figures 8 and 17. 



FIG. 33. Further stage of development of the spermatid, corresponding approximately to figure 10. 



FIG. 34. Interstitial cell. 



S4 



