69 



ard the '^harP'e of shn-^e of the dovplrrinr r'-bryc rre -^on- 

 rertcd •hcnorcna. The length of tire diirirp v;hirh thit: con- 

 dition IrvEtr ir> evidently cr^rr,ratively r.hort, for noon 

 cilia develor and the larva be.Pinr; to r.rvir. ^Stft Mean'"hilo 

 the rerirheral refTion of the cyncytiiin has been trancforred 

 into a distinct layer of ectoderral cells, se^arrted frc" the 

 inner rass cf tissue, etill rtrMrtin-eless ir character, by 

 the develorrent of the i^esoplcea. 



Frc- the fact that a syncytiu'^^ or rlas'-Ddiuit-lil'e 

 stmicture in for-ed, it is irrorsible to localize a-y of 

 the blastcreres cf the segr^ertinr ppr- ^vhich will for^- snecial 

 narts of the future embryo. Ever those cells v.-hich are at 

 the surface at the cr-rletion of serre^tatior car'-ot be 

 reparded as ^riritive ectoderm-, for i*' the brea--inp dov;n of 

 the cell boundaries, the forrration of the syncytiun, and the 

 recastinr of the cells it is quite ir^'^ossible to say '"hat 

 charpe cf the -protc-lasr ray take ■^lace. 



