PLATE 8 



EXPLANATION OF FIGURES 



Hydractinia echinata. X 85 



63 Centrifuged eggs, showing the direction of the first cleavage plane in 

 reference to the stratification. 



64 Sections of centrifuged eggs, showing the position of the nucleus in refer- 

 ence to stratification. 



65 Centrifuged eggs which were isolated and development to planula followed : 

 J and K show the resulting distribution of the materials in the planula. 



G6 Centrifuged eggs in which the blastomeres were separated in the two-cell 

 stage, isolated, and followed to the formation of the planula. F and G show several 

 stages in this development. 



250 



