142 JAMES O. FOLEY. 



EXPLANATION OF PLATES. 



Unless otherwise indicated the figures on plates i to 3 represent a magnification 

 of about 2160 diameters as they are reproduced. Figs. 7, 14, and 35 represent a 

 magnification of about 1650 diameters. A camera lucida was used for drawing 

 together with a 2 mm. oil immersion (Zeiss) and a No. 18 ocular (Zeiss). Drawings 

 51, 54, and 55, are from smears; the remainder, from sections. 



PLATE I. 



Fie. i. Ameboid cell of the migration period. 



FIG. 2. Resting cell of the spermatogonial growth period showing a prominent 

 chromatin nucleolus and twenty-one deeply staining chromatin bodies. 



FIG. 3. Spermatogonium showing seventeen chromatin bodies which appear to 

 be aggregation centers for the chromatin granules. 



FIG. 4. Middle spireme of spermatogonial prophase showing the chromatin of 

 the forming spireme in a beaded condition. 



FIG. 5. Polar view of spermatogonial metaphase showing nineteen long and 

 slightly contracted chromosomes. 



FIGS. 6, 7, 8, 9, 10, AND n. Polar views of spermatogonial metaphase showing 

 twenty-two chromosomes in varying degrees of contraction. Probable sex chromo- 

 somes indicated at (a) in figures. Fig. 7 magnified 1650 diameters. 



FIGS. 12 AND 13. Spermatogonial metaphase showing twenty- two transversely 

 constricted chromosomes. 



FIG. 14. Early anaphase of spermatogonium. Magnification 1650 diameters. 



