164 CHAS. W. METZ AXD JOSE F. XOXIDEZ 



EXPLANATION OF FIGURES. 



The figures were drawn with the aid of a camera lucida, using a Zeiss 2 mm. oil 

 immersion objective and number 12 ocular. Magnification about 1600 diameters. 



All figures except number 4 are from specimen number 2056. 



It should be emphasized that the figures represent cross sections at one level 

 in most cases, and do not represent entire nuclei. 



FIG. i. Spermatogonial metaphase, probably not entire. 



FIGS. 2-10. First spermatocyte growth period. 



FIG. 2. Very early growth stage. 



FIG. 3. Slightly later, nucleus becoming tabulated. 



FIG. 4. Later, but still in the early part of the growth period; nucleus com- 

 pletely transformed into narrow ramifying chambers. 



FIGS. 5-10. Various aspects of the nuclei during the successively later growth 

 stages, showing the lobes and chromosomes cut longitudinally, transversely and at 

 intermediate angles. The isolated portions in figures 8 and 9 are sections of lobes, 

 not separate vesicles. 



FIGS. 11-13. First spermatocyte metaphase in polar and lateral views, showing 

 the persistence of the hyaline cortical zone. 



FIGS. 14-15. Ptecticus (see text, p. 159). 



