190 



NUCLEOCYTOPLASMIC RELATIONS 



interest since they were able to demonstrate progressive differen- 

 tiation in the cortical cytoplasm before nuclei had migrated into 

 these regions. 



Of specific interest are the components of the cytoplasm that 

 contain the information necessary for direction of further devel- 



UV EXPOSURE (sec) 

 60 90 (20 150 



250 500 750 tOOO (250 1500 

 UV DOSE (ergs/mm^) 



Fig. 8. Dose-hatchability curves for Habrobracon eggs irradiated on 

 their convex (nuclear) surfaces (O, ultraviolet; •, ultraviolet plus photo- 

 reactivating light) or concave (non-nuclear) surfaces (A, ultraviolet; A, 

 ultraviolet plus photoreactivating light). From von Borstel and Wolff, 1955. 

 Proc. Natl. Acad. Sci. U. S., by permission of the University of Chicago 

 Press. 



opment. We assume ultraviolet radiation can destroy the ability 

 for progressive differentiation of regions on the periphery of de- 

 terminate eggs. 



The Habrobracon egg is unique inasmuch as ultraviolet irradia- 

 tion of the convex side of the egg kills the egg by damage to the 

 nucleus, whereas irradiation of any other place on the egg surface 



