LEE BARKER WALTON 149 



forms. The method of movement by means of the flagel- 

 lum furnishes a problem of considerable difficulty which 

 has received attention from several investigators, notably 

 Delage and Herouard (1896), Goodspeed and Moore 

 (1911), Biitschli and others. 



There are several inferences of an axiomatic nature 

 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 rel- 

 ative angle which the stride 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 methods 

 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 rotating 

 in the same direction that the earth rotates, conditions 

 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 development, 

 there are others which reproduce directly in the water 

 and should this have been the primitive condition 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 

 allow an interpretation in this direction. 



During the past two years a considerable number of 



