Nos. 622-623] ORGANIC EVOLUTION 



537 



that follow from such an hypothesis. Forms near the 

 neutral equatorial region may be assumed to possess a 

 slower rotation than forms near the poles and at the 

 same time there may be expected to occur a change in the 

 relative angle which the striae make with the longitudinal 

 axis of the body, their direction becoming approximately 

 parallel with that axis. The cosmopolitan distribution 

 of unicellular organisms with the evident non-selective 

 value of the character makes such a hypothesis difficult 

 of demonstration. The application of statistical meth- 

 ods would be of interest, however. 



A second explanation of the rotation direction, appar- 

 ently, however, a negligible one, is on the basis of the 

 angular velocity of the earth so far as it may have an 

 influence on small bodies at its surface. With free- 

 swimming microorganisms oriented in accordance with 

 the axis of the earth during definite intervals and rotat- 

 ing in the same direction that the earth rotates, condi- 

 lions are fulfilled for such a mechanical explanation. 

 When, however, the relative dimensions of the earth and 

 the organisms as well as the relative density of the earth, 

 the water and the organism, are considered, it is difficult 

 to believe that the explanation lies in this direction. 

 While many of the forms are attached to some definite 

 surface in the water during certain periods of their de- 

 velopment, there are others which reproduce directly in 

 the water ami should this have been the primitive condi- 

 tion of development, the rotation of the earth would have 

 been ineffective. 



While the possibility of electrical forces may be men- 

 tioned as an influence, there are no facts known which al- 

 low an interpretation in this direction. 



During the. past two years a considerable number of 



definite evidence as to the cause of the rotation. Obvi- 

 ously it would be of interest to maintain a culture of 

 northern forms in the southern hemisphere or a culture 

 of southern forms in the northern hemisphere. Efforts 



