216 PROCEEDINGS OF THE AMERICAN ACADEMY. ( 



PLATE II. 



Figures 7, 8, 9, 10, 13, and 14 are copied from Van Beneden et Julin's figures 

 of Clavelina Rlssoana. The otliers are of Ciona ; magnification, 400 diameters. 



Figure 7. Egg of Clavelina, 32-celI stage, with corrected orientation, ventral 

 view. (After Van Beneden et Julin's Fig. 9a). 



" 8. The same egg, dorsal view. (After Van Beneden et Julin's Fig. 9.) 



" 9. Egg of Clavelina, 44-cell stage, ventral view. (After Van Beneden 



et Julin's Fig. 10.) On the left side of the figure is given the 



corrected cell lineage, on the right side, the cell lineage according 



to Van Beneden et Julin. 



" 10. The same egg, dorsal view. (After Van Beneden et Julin's Fig. 

 10a.) On the right side of the figure is given the corrected cell 

 lineage, on the left, the cell lineage according to Van Beneden et 

 Julin. 



" 11 Egg of Ciona, 66-cell stage, ventral view. Only the marginal cells 

 of the ventral half have divided since the stage shown in Figures 

 5 and 6. 



" 12. The same egg, dorsal view. By more rapid division in the ventral 

 half of the egg certain of its marginal cells have been shoved 

 around on to this face of the egg Six marginal and anterior cells 

 of the dorsal half have also divided since tlie 46-cell stage. 



" 13. A nearly median optical section, parallel to the sagittal plane, 

 of the egg of Clavelina shown in Figures 7 and 8, with corrected 

 orientation. (After Van Beneden et Julin's Fig. 9c.) 



" 14. A nearly median optical section, parallel to the sagittal plane, of 

 the egg of Clavelina shown in Figures 9 and 10. (After Van 

 Benenen et Julin's Fig. lOc.) 



" 15. An actual transverse section of an egg of Ciona in the 32-cell stage. 



