60 



PROTOPLASMIC CONSISTENCY AND CELL DIVISION 



The following experiments are supplementary to the second. In 

 all of them the results obtained are explicable on the basis of the 

 existence, during cleavage, of reversible changes in the consistency 

 of the cytoplasm. 



s.oo 



5.3 S 



5.4-0 



5.4-5 



Fig. 8. Development of an Astcrias ovum manipulated with a needle so as 

 to suppress the first cleavage furrow, o, 5.00 p.m., disappearance of the amphi- 

 aster and obliteration of the cleavage furrow, b, 5.35 p.m., appearance of two 

 amphiasters. c, 5.40 p.m., change in shape of the ovum with appearance of 

 second cleavage furrow ahead of the first, d, 5.45 p.m., ovum cleaving into 

 four blastomeres. (The ovum developed into a normal embryo.) 



Experiment 3. — (Fig. 8.) In this case the first segmentation furrow 

 was prevented from forming by tearing at the equator whenever it 

 made its appearance. The progressive changes within the egg were 



