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



PLATE 77 



6c?^blastoderm 



6?2^nuclei of blastoderm 



r''=fourth cleavage plane 



ic^intercellular cavity 



/)=periblast 



pn^periblast nuclei 



*c=subgerminal cavity 



yz/=yo\k vacuoles 

 Fig. 24. Section thru 20-hour 32-celled disk showing jjeriblast 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. 



