3OO NATHAN FASTEN. 



9. DESCRIPTION OF PLATES. 



All the illustrations in the accompanying plates were made with the aid of the 

 camera lucida. Figs. 1-66 and 70-80 were drawn under Zeiss apochromatic objec- 

 tive 2 mm. Horn. Im. F Comps. ocular I2, 1 at a magnification of 2,720 times. 

 Figs. 6769 were drawn under achromatic lenses at an approximate magnification 



of 1,400 times. 



ABBREVIATIONS. 

 b = central body. 

 c = centrosome. 

 d = chromatin ring. 

 h = nuclear-mitochondrial cup. 

 k = chromatoid bodies. 

 m = mitochondria-like mass. 

 n = nucleus. 



r = r'ays or arms of spermatozoa. 



v = first or primary vacuole (first or primary vesicle). 

 z/ = second or secondary vacuole (second or secondary vesicle). 



EXPLANATION OF PLATE i. 



FIG. i. Resting primary spermatogonial stage. 



FIG. 2. Spermatogonial prophase, showing fragmentation of chromatin. 

 Within the cytoplasm two large, heavily staining masses, probably chromatoid 

 masses can be distinguished. 



FIG. 3. Late spermatogonial prophase. Note the compact chromatin clumps 

 within the nucleus. 



FIG. 4. Metaphase, primary spermatogonium. 



FIG. 5. Anaphase, primary spermatogonium. 



FIGS. 6 and 7. Telophase. primary spermatogonium. 



FIG. 8. Resting secondary spermatogonial stage. 



FIGS. 9 to 12. Nutritive cells. Observe the irregular nuclei and the fatty 

 globules within the cytoplasm. 



FIG. 13. Nutritive cell, in which the nucleus shows a constriction in the middle 

 which appears to be suggestive of amitosis. 



1 I wish to express my indebtedness and gratitude to the Department of Zoology 

 of the University of Wisconsin for the loan of a set of Zeiss apochromatic lenses 

 (2 mm. oil immersion objective and compensating oculars 4, 8 and 12), which were 

 of great service in the problem under consideration. 



