PLATE 3 



EXPLANATION OF FIGURES 



Camera drawings of sections. Magnification same as noted beiow. All 

 eggs are from Strongylocentrotus. 



16 and 17 showing the two types of monaster eggs found during the first divi- 

 sion cycle. X 1900. 



IS Detail drawing of aster. X approximately 3000. 



19 Monaster egg showing division of the centrioles. X 1500. 



20 Monaster egg showing division of the chromosome. X 1900. 



21 Monaster egg showing fusion of chromosome vesicle. X 1500. 



492 



