STUDIES ON REACTIONS TO STIMULI. 233 



one half the entire animal, whether taken from the anterior end, 

 the posterior end, the right or left side, or the middle of the 

 body. It is true, whether the piece does or does not bear any 

 of the oral or other differentiated cilia. 



These results establish the following facts : 



1. The turning toward a structurally defined side after stimu- 

 lation is not produced alone by the oral or peristomal or anterior 

 cilia, or by any particular set of cilia, since it takes place in pieces 

 of the body containing no specially differentiated cilia. 



2. The swerving toward a certain side in the spiral swimming 

 is not due alone to any special set of cilia, since it occurs in pieces 

 from any part of the body. 



3. The swerving toward a certain side is likewise not due to 

 the geometrical form of the body (as to a groove on one side, 

 such as we find in Paramecium), for it continues when the form 

 of the piece is essentially altered (as by the removal of the oral 

 groove in Pafamecium). 



4. The revolution on the long axis in a certain direction, while 

 swimming, is not due to any special set of cilia, nor to any pecu- 

 liarities of form of the body, since it occurs in pieces from all 

 parts of the body. 



5. From the foregoing paragraphs, 1-4, it must be concluded 

 that the revolution on the long axis, the swerving toward a 

 defined side in the spiral course, and the turning toward a struc- 

 turally defined side when stimulated, are due to the method in 

 which the cilia strike. This peculiar (one-sided) stroke is not 

 limited to any particular set of cilia, but is shared by all the 

 body cilia. 



Division of labor is thus not marked, so far as these points are 

 concerned, among the locomotor organs of these animals. As 

 'any portion of a crystal is organized like the entire crystal, so in 

 the Ciliata any piece of the body, apparently, is organized so as 

 to move and to react to stimuli in the same manner as does the 

 entire animal. 



