CCELOMIC SACS 



Fio. 1. — Sections through one of the 

 EsTEROCCELA (ft Scyphistoiiia polyp) 

 to show the Sacculation and Con- 



TINUITV OF THE ARCHENTERON AND 



THE TWO Primary Cell-layers. 



0I-, ectodenu, and en, eiidoderm, indi- 

 cated by dark and pale shading re- 

 spectively. A, sagittal section of the 

 diblastula embryo without oral aperture ; 

 B, similar section of the young polyp 

 after fixation but without oral aperture. 

 », oral in-sinking (stomodicuin) ; g, meso- 

 gloea. C, young polyp with mouth. sTp, 

 junction of stoniodieiun and archenteron ; 

 7)1, gastric pouch. D, transverse section 

 taken so as to cut tlie gastric pouches 

 (w) above their openings into the archen- 

 teron ; s, stomodiiium. E, a similar 

 section at a later period when four 

 pouches have been formed, sf, septa. 

 F, transverse section at a lower level, 

 showing the continuity of the gastric 

 pouches with the axial portion of the 

 archenteron ; i, tieniolas. (After Goette, 

 from Korschelt and Heider.) 



Fio. 2.— Sections through the Lauv.e of an Echinoderm (Astcriiia gibbosa) at Suc- 

 cessive Stages of Growth ; A, B, C, to show the Origin op the C(elom as a Pair 

 OF Enteroccelous Pouches. 



7.7, Blastopore ; Z), archenteron ; Vj>, vasoperitoneal .sacs or coelomic pouches, r and /, 

 right and left sides. (After Ludwig, from Korschelt and Heider.) 



