of clor.vnf.c cavity, thr r.ur.erf icial crlln of which nro con- 

 vrrtrd irto thr ectodrrral layer, vrhilr those within re- 

 present the endodern. Here thf t;\'0 layers ere forred direct- 

 ly v.-ithout the fcrratior of a syncytial structure, 



Ir Eudendriur and Fenrar.ia acccrdirp tr Harritt's 

 descri-^-tior a condition screwhat si'-ilar tc thnt of Turri- 

 t ops is is found. He says: "Indeed ir both FudendriuTr and 

 Perraria, not tc rention other cases, cleavage v^ould 

 seer to result primarily in the fcr-ation of a rcre or less 

 characteristic syncytiun^, the subsecuent develerrert of the 

 perr layers tr.l:inf r]ace by a gradual differentiation of the 

 syncytial elererts, first ard naturally the ectcderr, and 

 later, often very '■'uch later, the enuoder-." 



The syncytia ijcharacter in Turritc-sis is acquired 

 under favorable conditions, whe- the cnbryo is about six 

 hours old; at the •'. i"-e that the irrcf^ular rass of ser- 

 rfntinn cells is retaromhosed in to the oval embryo. And 

 I a- inclined to thin'- that the for-ation of the syncytium 



