114 SAKYO KANDA. 



admitted changes in specific gravity had occurred, due to loss of 

 water. If this loss were chiefly from the posterior part, the 

 changed orientation would be explained as a passive instead of an 

 active process. The writer, therefore, holds still that these 

 animals, when strongly centrifuged, are passively thrown with 

 their anterior ends away from the axis of the centrifuge. There- 

 fore, the anterior end is heavier. The negatively geotropic 

 orientation in the normal animals is, therefore, an active process 

 and the mechanical theory is not correct. 



McClendon "found the time elapsing before the return of the 

 negatively geotropic reaction to roughly correspond to the time 

 required for the return of the nuclei to their normal position." 

 The writer also found that this was the case. According to 

 McClendon, "this might indicate that nuclei in normal position 

 acted as statoliths." It is hard to decide for or against this for 

 at the time of "the return of the nuclei to their normal position," 

 other heavy substances, "phosphate crystals," for instance, 

 which were precipitated in the extreme anterior end of the animal 

 seem, also, to distribute in their original position. In other 

 words, about at the time of return of the nuclei to their normal 

 position, all the protoplasmic substances of the animal, which 

 were disturbed by the centrifugal force from their original dis- 

 tribution, recover from the disturbance. The result is that the 

 animal resumes the negatively geotropic reaction. Such con- 

 sideration may suggest that the whole organism in normal con- 

 ditions acts as a "statecyst," and all the heavy substances as 

 "statoliths," not merely the nuclei. Here lies the significance 

 of Lyon's conception that "for internal stimulation the relation 

 of the parts of the cell to each other must be changed in some way 

 by gravity. Stresses or pulls which occur when the organism is 

 in one position with respect to the vertical, must be changed in 

 another position." For the present we cannot decide in favor 

 of any particular organ or constituent of the cell as the basis of 

 the reaction. 



3. Does temperature reverse the negative geotropism of Para- 

 mecium caudatum? 



From his observations on the effects of raising and lowering 

 temperature on the geotropism of this animal, Sosnowski con- 



