PLATE 3 



, EXPLANATIOX OF FKiURES 



9 to "20 form a developmental chart, showing; the comparative rates of devel- 

 opment of embryos of pure F. diaphanus (middle column) and the two types of 

 F. diaphanus egg hybrids (that from F. majalis sperm on the left and that from 

 F. heteroclitus sperm on the right). Note that F. majalis sperm retards early 

 development and that F. heteroclitus sperm as markedW accelerates it. 



494 



