32(5 



Vdriatioii and Correlatlon in Arcella 



What we have then as material for this bioinetrical study is a randoni sample 

 of the individiials of a populatiou of Arcella, covcring a period of aboiit three 

 weeks in the life of the culture. It inay be cousideied that we have a section 

 tliree weeks long in the cultural history, and have investigated the conditions of 

 the individiial Arcellue falling within that soctinn. 



III. Results. 



A. Variation in Outer und Inner Diameters. 



The results of the nieasurements of the outer aml inniT diameters of 504 iinli- 

 viduals are shown in Tables I and II. 



TABLE I. 



Onter Diameter. Class unit = 2 mikrons. 



TABLE IL 

 Inner Diameter. Class unit = 1 niikron. 



