28 CELLULAR 



take place the more readily as the external solu- 

 tion becomes more acid. 



While these studies were being made on 

 Nitella The Rockefeller Institute for Medical 

 Research very generously made it possible to 

 carry on investigations on the marine alga Va- 

 lonia. This forms large multinucleate cells, 

 shaped somewhat like a balloon, containing up 

 to 10 cubic centimeters of sap. The sap is desti- 

 tute of the motion observed in Nitella; it is sur- 

 rounded by a delicate layer of protoplasm con- 

 taining chloroplasts and numerous nuclei: this 

 is surrounded by a cellulose wall. 



The use of large cells enables us to find out 

 what goes on inside to a greater extent than was 

 previously possible. As a result of these studies 

 I have formed quite different conceptions of the 

 behavior of the interior of the cell from those 

 which I previously entertained. It has become 

 apparent that we must now restate our problems 

 and begin a fresh attack upon the whole subject. 

 Although it is too soon to try to picture these 

 new conceptions with any degree of complete- 



