3O6 L. J. BACHHUBER. 



EXPLANATION OF PLATES. 



All drawings made with camera lucida. Spencer 2 mm. apochromat oil 

 immersion objective and X 16 compensating eye-piece used. All drawings ar- 

 shown at a magnification of approximately 1,800 diameters. Drawings are 

 accurate with reference to the nuclear material and the chromatoid body and their 

 position in the cell; the cytoplasm, however, is represented conventionally. S, 

 Sertoli cell; C, chromatoid body. 



PLATE I. 



FIG. i. Sertoli cell, showing the relation of the metamorphosing spermatosomes 

 to the nurse cells. 



FIGS. 2,3. Early stages of the spermatogonia with the two large karyosomes. 

 Fig. 2 also shows the slender fibrillae in the cytoplasm. 



FIGS. 4, 5. Later stages of the spermatogonial nuclei showing the linin threads 

 radiating out towards the periphery of the nuclear wall. 



FIG. 6. Shows the only spermatogonial cell in which a body was found which 

 resembled the chromatoid body. 



FIG, 7. In this stage a condensation of the nuclear material is taking place, 

 forming masses which later transform directly into the chromosomes of the sperma- 

 togonia. 



FIGS. 8-10. Metaphase stages of the spermatogonia showing the probable 

 twenty-two chromosomes. Fig. 10 is taken from a smear preparation. 



FIG. n. Shows the divided chromosomes passing towards the poles. The X 

 and the Y elements cannot be identified at this stage. 



FIG. 12. Prophase of the primary spermatocyte showing the chromosomes 

 from the previous division weaving oat into fine strands which immediately spread 

 through the nucleus. 



FIGS. 13-15. Synezesis stages of the primary spermatocytes showing the 

 massing of the fibers, accompanied by a slow condensation, as shown in Fig. 15. 

 This also shows the two accessory elements, which retain their spherical shape, 

 while the ordinary chromosomes weave out into the leptotene threads. 



