Castle. — Ciona intestiuaiis. 



PLATE II. 



Figs. 7-10. Four sections through an impregnated egg ; magnification, 560 diam- 

 eters. 



Fig. 7. Fourth section of series, showing the male pronucleus and archoplasmic 

 spheres. Compare Figs. 11 and 12. 



Fig. 8. Seventh section of series, showing the female pronucleus. 



Fig. 9. Tenth section of series, showing the female archoplasm. 



Fig. 10. Twelfth section of series, showing polar globules. 



Fig. 11. Graphic reconstruction of the series on a plane, perpendicular to that of 

 Fig. 7, indicated by the line a b, Fig. 7. 



Fig. 12. A similar reconstruction on a perpendicular plane, the projection of 

 which is the line a' b', Fig. 7. 



