AUTHOR S ABSTRACT OF THIS PAPER ISSUED 

 BY THE BIBLIOGRAPHIC SERVICE, NOVEMBER 7 



PROTOPLASMIC VISCOSITY CHANGES DURING 



MITOSIS^ 



L. V. HEILBRUNN 



ONE CHART 



THE PROBLEM 



Earlier work showed that the segmentation of the sea-urchin 

 egg and the appearance of the mitotic spindle in this egg depend 

 upon a viscosity increase in the cytoplasm (Heilbrunn," 15, 

 '17, '20). During mitosis protoplasmic viscosity changes were 

 demonstrated. It is of interest now to inquire whether similar 

 viscosity changes occur in the dividing eggs of other forms. 

 If the mitotic mechanism depends upon viscosity changes, then 

 such changes should be present in all dividing cells. Further- 

 more, it has been thought advisable to determine more accurately 

 the magnitude of these changes. 



Most of the work was done with the Cumingia egg, although 

 some data from the sea-urchin and Nereis eggs is included for 

 the sake of comparison. The Cumingia egg is immature at 

 fertilization and therefore offers an interesting comparison to 

 the egg of the sea-urchin. In Cumingia, three cell divisions 

 occur in a short space of time between fertilization and the first 

 cleavage. Do viscosity changes accompany these divisions and 

 do they show the same time relation to the mitotic process that 

 was previously demonstrated for the sea-urchin egg? 



At Woods Hole Cumingia tellinoides is fairly common, and 

 during the summer of 1920 good material was generally available 

 throughout July and August. My thanks are due to Prof. 

 F. R. Lillie, director of the Marine Biological Laboratory, for 

 the privilege of carrying on the work there. 



^ Contribution from the Zoological Laboratory of the University of Michigan. 



417 



