104 EDMUND B. WILSON 



PLATE 1 



EXPLANATION OF FIGURES 



All the figures from photographs of sections. Enlargement 1500 diameters. 



10, 11 First spermatocyte-division (N. hilaris) 



12, 13 The same (N. viridula) 



14, 15 Second spermatocyte-division (hilaris) 



16-25 Side views of second division (hilaris) . The XY-pair shown in 16-23, the 



d-chromosome in 16, 17, 20, 24, 25; the small chromosome is evident in 



10, 12, 13, 14, 15, 17, 18. 



22 Initial separation of X and Y 



23 Early anaphase, X and Y separating near the center (hilaris) 



26-28 Nuclei from the growth-period, showing chromosome-nucleolus and plas- 



mosome (hilaris) 

 29 Corresponding stage (viridula) 



