294 ELIZABETH A. SMITH. 



PLATE II. 



Sympetrum semicinctum (Say). 



FIG. 3. Part of a cyst showing degenerating spermatogonia. 



FIG. 4. A group of spermatogonial cells. 



FIG. 5. A spermatogonial cell from a smear preparation. 



FIG. 6. Polar view of spermatogonial chromosomes from an aceto-carmine 

 smear. 



FIG. 7. Polar view of metaphase of spermatogonial nucleus in which only a 

 few chromosomes are in focus. 



FIG. 8. Polar view of metaphase of spermatogonial nucleus. 



FIGS. 9, 10, AND n. Telophases of spermatogonial divisions. 



FIGS. 12 AND 13. Polar views of telophases of last spermatogonial division. 



FIGS. 14, 15, AND 16. Spermatogonia with the round, dense body that 

 may correspond to the mass in the growth period which subsequently becomes the 

 sex-chromosome. 



FIG. 17. Spermatogonia in the diffuse period before the growth changes begin. 



FIGS. 18, 19, AND 20. Massive bodies in the nuclei at the beginning of growth 

 period. One mass which later forms the sex-chromosome is much darker and 

 more compact and is marked X. 



