36 J. E. WODSEDALEK. 



PLATE II. 



(All of the drawings on plates 2-6 were made with the aid of a camera lucida. 

 X2.330.) 



16. Early spermatogonial cell showing two large nucleoli. The cell boundary 

 is quite indistinct. 



17. Resting stage of a full grown spermatogonial cell showing two large and two. 

 small nucleoli. 



18. Late prophase of a spermatogonial division showing eighteen chromosomes' 

 The two large oval chromosomes at the top are apparently the accessories. 



19. Metaphase of division in a spermatogonium showing the two divided ac- 

 cessories at the right. 



20. Early resting stage of a primary spermatocyte showing the centrosome, 

 two large, and several small nucleoli. 



21. Primary spermatocyte in synizesis. 



22. Primary spermatocyte following synizesis and synapsis; the entangled mass 

 of threads moved toward the center of the nucleus and the threads appear to be 

 twice as thick as those in the synizesis stage. 



23. Primary spermatocyte following the synaptic stage. The clear area in the 

 nucleus disappears and the nuclear wall becomes well developed. 



24. Spireme stage of a primary spermatocyte showing increase in size of both 

 the nucleus and the cytoplasm and also the two large nucleoli. 



25. Breaking up of the spireme into U and variously shaped chromosomes. 

 The two nucleoli become oval in shape and can always be seen close together in 

 this stage. 



26. 27 and 28. Late prophases of primary spermatocytes showing ten chromo- 

 somes. The two oval accessories, which are smaller than the bivalent autosomes, 

 are shown in characteristic positions. 



