3IO L. J. BACHHUBER. 



PLATE III. 



FIG. 29. Again showing the accessory elements migrating towards the poles 

 in advance of the ordinary chromosomes. 



FIG. 30. A stage following division of the chromosomes of the primary sperma- 

 tocyte showing the eleven chromosomes at the pole, the accessory in the center. 



FIG. 31. Shows the chromatoid body migrating in between the two sets of 

 chromosomes immediately after division. 



FIGS. 32, 33. These cells give evidence of a precocious division of the X and 

 the Y elements. In this case, two X elements and two Y elements travel towards 

 the poles. 



FIG. 34. The chromosomes of the secondary spermatocytes have immediately 

 lined up in the equatorial plate stage, ready for the next division. 



FIG. 35. The chromosomes of the secondary spermatocytes divide and pass 

 to the poles in ring-like masses, practically losing their identity as individual 

 elements. This stage also shows the chromatoid body. 



FIG. 36. Shows the chromosomes after reaching the poles and before formation 

 of the spermatids. The chromatoid body is still present. 



FIGS. 37, 38. Show the occasional identification of the accessory elements in 

 the center of the closely interwoven mass of chromosomes, giving a ring-like 

 appearance. 



FIGS. 39, 40. Condensation of nuclear material at the periphery of the nuclear 

 wall. Also shows the presence of the chromatoid body. 



FIGS. 41-43. Further condensation of chromatin around the periphery of the 

 nuclear wall. The centrosome is meshed in one side of the nucleus. The chroma- 

 toid body may lie in any portion of the cytoplasm and may be very irregular in 

 shape. 



FIGS. 44-46. Still further condensation, with the gradual escape of the nucleus 

 from the excess cytoplasm. The chromatoid body is cast off with the excess cyto- 

 plasm. 



FIGS. 47, 48. Show the presence of darker staining masses of chromatin 

 material which may represent the individual chromosomes in the sperm head. 



FIGS. 49, 50. The darker staining masses now diffuse through the sperm head 

 and finally form an even-staining mass of chromatin. 



FIG. 51. Fully developed spermatozoon, showing the head, the middle-piece 

 with the centrosome, and the long, thin, lightly staining sperm tail. 



