470 THEOPHILUS S. PAINTER 



sions were not permanent as a rule. On examining these eggs 

 with high powers I was unable to detect the presence of any 

 radiations in the cytoplasm, although in the central clear area 

 of the egg, a few very faint fibers were visible. A study of 

 the treated eggs was undertaken in order to find out the changes 

 which preceded this cytoplasmic division, with the hope of 



- A 



. \ 6i 







Fig. H 



being able to throw light on the cause of the protoplasmic move- 

 ment in the monaster eggs. 



The present experiments were carried on at Woods Hole 

 and the material used was the eggs of Arbacia punctulata. 

 After fertilization, the eggs were allowed to undergo develop- 

 ment for five to fifteen minutes and then they were placed in 

 a 1/2000 n solution of phenjd urethane in sea water. The 

 eggs were followed under the microscope, and portions both of 

 the controls and of the experimented eggs were preserved at 

 ten minute intervals either in strong Fleming or in sublimate 



