55 

 •ivative of a structur Li . .Ill, 



falls steeply into :he outer periblast f o.p . ) . the cells 

 ore all r uclei. are 



i 

 periblast f c.p .) . Sea 



of the cells. The mitotic figures indicate that division 

 into the next . 



In Pi . 59, " 

 section is si- 

 one cell 



i 



In the central section t] :ion cav- 



il. ( s.c . ) bee 'ger. The outer ceils are 



flattened on ior, le structure is v 



- . 55, 



Stage of One-hundred- twenty- eight Surface Cells, 

 The normal gently arched type is represented in Fig. 

 a nearly central section of a blastoderm of this stage. The 

 central periblast ( c ,p . ) is here thick and fairly -.'ell de- 

 limited from the yolk below. Of especial interest 'are the 

 cells in ' cut out of it into the segmentation 



cavity, ' r eny notable is I cy of vacuoles (v.) in this 



