338 Puget Sound Marine Sta. Pub. Vol. 1, No. 28 



PLATE 77 



6c?^bla.stoderm 

 6«^nuclei of blastoderm 

 r*^fourth cleavage plane 

 ir^intercellular cavity 

 p=periblast 

 /7W^=periblast nuclei 

 Ac^subgerminal cavity 

 i/zr=jolk vacuoles 

 Fig. 2i. Section thru 20-hour 32-celled disk showing periblast with- 

 out periblastic nuclei. X50, 



Fig. 25. Section thru 32-hour disk. X 50. 



Fig. 26. Section thru 101 -hour disk showing blastoderm, segmenta- 

 tion cavity, and periblast with scattered nuclei. X 50. 



