Davenport — Cerata in .^^olis. 



PLATE II. 



ABBREVIATIONS. 



Mesoderm lining body wall. 

 ]\Iesoderni lining hepatic 



coecum. 

 Neinatocyst, smaller kind. 

 Developing nematocyst. 

 Nematocyst, larger kind. 

 Foot. 

 Penis sac. 

 Pvadula. 

 Khinophore. 

 Rectum. 

 Testis. 

 Ureter. 

 ., 9. (?• Lobes of ovary and 



testis. 



;. 9-11. Three stages in the development of the cerata. Vertical sections 

 X 120. 



12. Longitudinal section of ceras just before formation of external opening of 



cnidophore. X I'^O. 



13. Transverse section of adult cnidophore, showing nematocysts. X 405. 



14. Bit of transverse section of hepatic ccECum, showing fully formed and 



developing nematocysts in hepatic cells. X 405. 



15. Bit of transverse section of hepatic coecum, showing large nematopliore. 



X 405. 



16. Longitudinal section of young JEolis, inclined about 30° from vertical, 



passing through axis of alimentary tract and first ceras of tliree trans- 

 verse rows. X 70. 



17. Enlarged view of the posterior of the two regions marked by asterisks in 



Figure 16, but from a section adjacent to Figure 16, showing parietal 

 mesoderm, some of which is about to form that of the youngest trans- 

 verse row, and some to give rise to sexual cells, te. X 318 



18. Longitudinal section of young ^Eolis. Oblique in front, nearly frontal 



behind. Showing repetition of sexual organs and their relation to 

 transverse rows of cerata. X 76. 



