Davenport. — Uerata in JEolis. 



PLATE I. 



ABBREVIATIONS. 



Stomach. 



Prolongation of stomach back- 

 wards. 



Gastric diverticulum at base of 

 transverse rows of cerata. 



Mesenchyme of developing 

 ceras. 



(Esophagus. 



Foot 



Kectum. 



Figs. 1, 2. Two figures of young individuals of JEolis sp., showing arrangement 

 of cerata in transverse rows, which are numbered with Roman 

 numerals. X 5. 



" 3. Transverse section of a young j^olis showing the stomach, the gastric 

 diverticulum, and hepatic coeca of a transverse row of cerata. X 45. 



" 4 Outline of alimentary tract of ^olis, copied from Alder and Hancock, show- 

 ing gastric diverticula and points of connection of hepatic ccrca. 



" 5-8. Four vertical sections through different stages in the development of the 

 cerata. 



" 5. First stage in formation of ceras. Mesenchyme thickened at ms'chy. 

 Right side. X 405. 



" 6. Second stage in formation of ceras. Mesenchyme thickened still further. 

 Ectoderm beginning to evaginate in the axis. Left side. X 405. 



" 7. yiiird stage in formation of ceras. Gastric diverticulum beginning to out- 

 fold to fonu hepatic coecum of new ceras. Left side. X 228. 



" 8 Fourth stage in formation of ceras. Right side. X 228. 



