PLATE 2 



EXPLANATION OP FIGURES 



21 First spermatocyte. Nucleus homogeneous except for idiochromosomes. 



22 First spermatocyte showing fine, loosely arranged leptotene thread. Idio- 

 chromosomes very pale in color. 



23 Early contraction stage of first spermatocyte. Plasmosomes with idio- 

 chromosome thread to one side. 



24 First spermatocyte showing a spreading out of the threads following con- 

 traction. Plasmosome and idiochromosome threads shown in surface view. 



25 Bouquet stage of first spermatocyte. Only a few loops shown in drawing. 



26 Pachytene stage of first spermatocyte. 



27 Same as the preceding, only somewhat later. 



28, 31, and 34 Sertoli cells associated with different stages in the development 

 of the spermatozoa. 



29 Confused or net-like stage of first spermatocyte. Planosome prominent. 



30 Early prophase of first spermatocyte. Centrosomes have migrated nearly 

 to poles. Two plasmosomes present. 



32 Dividing cell from spermatogonial region. Possibly a Sertoli cell. Chro- 

 mosomes paired. 



33 Diagram to show the relative sizes of cells of first and second maturation 

 divisions and of the spermatid. 



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