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GRACE MEDES 



the following day a small percentage of individuals with skele- 

 tons represented by small heavy tri-radiate spicules The 

 specimens in solution c (fig. 77) were irregular and abnormal 

 looking and were moving about slowly on the bottom of the 

 dish. Gastrulation had begun, but had proceeded only a little 



Figs. 75 to SO. Experiment 10. NaHCOa. 



Fig. 75 10a, 24 hrs. Control. 



Fig. 76 106, 24 hrs. Gastrulation. No skeletons. (Optical section.) 



Fig. 77 10c, 24 hrs. Gastrulation just commenced. No further develop- 

 ment. (Optical section.) 



Fig. 78 lOd, 24 hrs. Blastula. 



Fig. 79 lOe, 24 hrs. Morula-like mass of cells. 



Fig. 80 10/, 24 hrs. Morula-like mass of cells in less advanced stage of 

 development. 



way and the walls presented a rough and uneven appearance. 

 In the other three solutions (figs. 78 to 80) all were dead, d 

 (fig. 78) after reaching the blastula stage, and e and /, a late 

 cleavage. In e (fig. 79), the smaller cells indicate a slightly 

 more advanced stage than in J (fig. 80) , but both have become 

 irregular, morula-like masses. 



