174 M - LOUISE NICHOLS. 



EXPLANATION OF PLATE I. 



The drawings were made with the camera lucida, Zeiss microscope, oc. 12, obj. 

 oil immersion 1/12. They have been enlarged to twice the diameter and reduced 

 one half. 



FIGS. 1-4. Spermatogonia. Prophases. 



FIGS. 5-7. Last generation of spermatogonia. Prophases. 



FIGS. 8-0. Synapsis. 



FIG. 10. Resting spermatocyte. 



FIGS. 11-18. Spermatocytes. Prophases of the first maturation division. 



FIGS. 19-20. Equatorial plates of the first maturation division. 13 chromo- 

 somes. 



FIGS. 21. The heterochromosome x. 



