PLATE III. 



1 8. Tangential section of disk of Cribrina artemisia 



(Leitz I, 3, camera). 



19. Transverse section of perfect mesentery of Cribrina 



artemisia (Leitz I, 3, camera). 



20. Transverse section of basilar muscle of Cribrina arte- 



misia (Leitz I, 3, camera). 



21. Portion of upper part of a perfect mesentery, with 



disk, margin, and upper part of column in section, 

 of Anthopleura xanthogrammica ; ac = acrorhagus ; 

 sp = sphincter ; / = tentacle. ( X 6. ) 



22. Transverse section of sphincter oi Antlwpleiira xantlio- 



grammica (Leitz I, 3, camera). 



23. Transverse section of primary mesentery of AntJio- 



pleura xantJiogrammica (Zeiss a, Leitz IV, camera). 



24. Transverse section of basilar muscle of Anthopleura 



xanthogrammica (Leitz I, 3, camera). 



25. Epiactis prolifera from a preserved specimen. Em = 



adherent embryo (nat. size). 



26. Transverse section of sphincter of Epiactis prolifera. 



L = lower extremity of section ; U^ upper ex- 

 tremity. (Leitz I, 3, camera). 



27. Transverse section of a portion of the column wall of 



Epiactis prolifera, with an adherent embryo. Ec = 

 column ectoderm; E.ec =^ ectoderm of embryo; 

 i5".(f;r= endoderm of embryo ; J/ == mucus; St =^ 

 stomatodaeal invagination. (Leitz I, 3, camera). 



28. Transverse section of perfect mesentery of Epiactis pro- 



lifera. (Zeiss a, Leitz II, camera). 



29. Transverse section of basilar muscle of Epiactis prolifera 



(Leitz I, 3, camera). 



(52) 



