these atrvcfjrcs in the castrulac o -^ Phorcrii::^ Kowalevskii but 

 Lonj^chajnts (1^~), wi.o i^as receutly carefully stuaied. tne same 

 bpecies, has been unable tc find them, Ikcaa (9), hc.vever, 



'inds very definite aivcrticula in the gastrulae of Phoroids IJi- 

 iTiai but he fii-aires tliem as being in tiie region of the blastopore, 

 '.vhile according to Caldwell's (3a) figures, tney are found 

 posterior to tne d1 as to pore. 



Let us return a^ain to t::e mesoderm cells which lie anter- 

 iorly to the blastopore, ThOde amoeboia celo^s unaoubt edly r:.ul- 

 tiply v.hile iii the bias toco el and in a j_astrula v.he re tr.e blas- 

 topore lips have closed up somewhat so as to give an oval out- 

 line to ti:e blastopore (Fig, 16(f) ), these cells have becorae 

 arranged into a definite sac- ( '^''it^s. 19-ijO (a) ) which is later 

 to fomi the linin^-. of U:e i.reoral lobe, Iii no ease was I abxe 

 tc fina ti;e loaat liidication cf an aiiterior unpairea divertic- 

 ulum which Masterman (16) uc^yo exists in the gastmlaof Ph^- 

 ronis Euskii. At ti.is stage the cavity o f tne sac is small 

 and is present only in lY-ont of the blastoporri. The v/alls 

 however, are extended on each side into a lateral cora of mes- 

 oderm cells which lies in the blastocoel at tnc side of the 

 blastopore. (Fig. 16(f) ) Soiae of tne cells of tne dorsal wall 

 of the sac. sem out pseudopodia vAiich attach themselves to an oc- 



todern.al thici;eni_ng and this thici-emngwi H become the ganglion 



