314 J- E. WODSEDALEK. 



EXPLANATION OF PLATES. 

 PLATE I. 



(All of the drawings were made with the aid of a camera lucida, X 2,400.) 



FIG. i. Early spermatogonial cell showing a large triangular nucleolus and two 

 small nucleoli, one of which is spherical. Other cells in the same stage often show 

 many more nucleoli. 



FIG. 2. Resting stage of a full grown spermatogonial cell showing the large 

 triangular nucleolus and several small nucleoli, one of which is spherical and can 

 frequently be detected. 



FIG. 3. Prophase of a spermatogonial division in which the chromosomes are 

 still rather indistinct. 



FIGS. 4 AND 5. Late prophase of spermatogonial division showing thirty-six 

 ordinary chromosomes and the large accessory which can easily be distinguished. 



FIGS. 6 AND 7. Metaphase of division in a spermatogonium showing the accessory 

 dividing in advance of the other chromosomes. In Fig. 6 the cell appears smaller 

 and the chromosomes are more crowded. 



FIGS. 8 AND 9. Early and late resting stages of a primary spermatocyte. re- 

 spectively. Both show the large and the small nucleolus. 



FIG. 10. Primary stage just before synizesis showing a mass of fine threads 

 and the two nucleoli. 



FIG. n. Primary spermatocyte in synizesis showing the nucleoli in a char- 

 acteristic position out of the mass of threads. 



FIG. 12. Primary spermatocyte following synizesis and synapsis. The threads 

 scatter about in the nucleus. 



FIGS. 13 AND 14. Spireme stage of a primary spertnatocyte showing increase in 

 size of the cytoplasm, nucleus and the large nucleolus, and the beginning of the 

 chromatoid body. 



