ROBERT CHAMBERS 



63 



behind the normal controls. By the next morning it had developed 

 into a swimming blastula not to be distinguished from the normal 

 controls. 



The obliteration of the cut and of the furrow is consequent to a 

 reversal of the egg cytoplasm from a semirigid to a more fluid state. 

 The fihn projecting into the egg gradually merges into the liquid 



Fig. 10. Successive stages of an Asierias ovum showing persistence of a puncture 

 made below the first cleavage furrow as it is beginning to form. 



cytoplasm surrounding it and surface tension forces finally overcome 

 the deformation of the egg. The egg now proceeded to divide into 

 four blastomeres as in Experiment 3. 



Experiment 5: — (Fig. 10.) This experiment demonstrates a pecu- 

 liar property of the equatorial region during the formation of the 

 cleavage furrow. A tear was made through the egg below the seg- 

 mentation furrow (Fig. 10 a). The hole produced by the tear 



