EMBEYONIO fISSION IN CYCLOSTOMATOUS POLYZOA. 43 



PLATE III. 



Fig. 15. — Crisia eburnea. A young internode decalcified, with a develop- 

 ing ovicell. For explanation of the letters (a, b, and c) see p. 5 (Zeiss, A). 

 Figs. 16— 23.— C. ramosa. 



Fig. 16. The aperture of the same ovicell from which Fig. 6 was taken. 



The origin of the giant-cells from the thickened distal end of the 



tentacle-sheath is shown (Zeiss, F). 

 Fig. 17. Longitudinal sectioDi of an ovicell which is filled with secondary 



embryos. To the left, the primary embryo (Zeiss, A). 

 Fig. 18. Protoplasmic reticulum with giant-cells, from an ovicell at about 



the stage of Fig. 11 (Zeiss, F). 

 Figs. 19 — 21. Development of ovicell (Zeiss, A). The ovicell has in each 



case been numbered 4, in order to admit of ready comparison between 



the three stages. 

 Fig. 22. Toung secondary embryo, in longitudinal section (Zeiss, F). 

 Fig. 23. Older embryo, in longitudinal section (Zeiss, F). 



