21 



is rorf ranic ir the rr.pior v.-here the pr^dndorir is river 

 off, ard ccnsecuently the cells v.Tuld be ^arrovjor. U^- 

 fortnrr.tely , because of scarcltj^ cT raterial, the exact 

 cellulrr details cf the for-atio- of the e-doderr v;ill 

 have tr be left for future study. 



The ripration of the erco'er'' ccrtirues frr scFe 

 hcurf^ , ard firally the blastccrel(\brcr'-es sclidl^'- filled 

 v;ith this nev/ly developed tissue. At first the cells are 

 crowded tof^ether, frecue'^tlv q-dte dersely, without any 

 definite arrarpe-^er.t except that due to rressure. Ther 



those cells that are situate'" next to the e'^tc-ler'^al layer 



e 



cha-fTc i* sha'^e, beco"-«=wF colu-nnr a-d assu^^e the a^'-earance 



of a "ore or less cistinot layer. Such an arranf^ene-^t is 

 shov/n i-- Figure 22. Later a seriaration talces rlace in 

 the centre of the en^derrral -ass. This is the first be- 

 pin-'inr cf the coelenteric cavity, v'hjch Pra-Uially in- 

 creases in si:?e; and finally the c-dcderral cells oecoTe 

 arranped in a sinrle layer around this cavity. 



