RESPONSIVE LIFE OF ORGANISMS 



439 



perception is by such an organ enormously increased. This 

 fleck of pigment in Euglena is the rudiment of an organ, pos- 

 sessing increased sensibility to light ; and it is doubtless no 

 more an accident that it should lie in the front end of the 

 body, than that a vertebrate's eyes should be located in its 

 head. 



Some reactions of Paramoecium. Improvements in the 

 organization of the body of Paramcecium are by no means 

 confined to the development of cilia. These are but 

 specialized parts of the ectoplasm, which depend largely for 

 their efficiency on further differentiation of other parts of 

 it. The general outer surface of the ectoplasm has become 

 thickened, giving permanence of form to the body and 

 solidity of support for the cilia. In the underlying ecto- 



FIG 257. Diagrams of behavior in Paramoecium. a. the avoiding reaction; / tod. 

 successive positions: arrows indicate ' directions of movement, b the contact 

 reaction. (After Jennings) 



plasm are developed strands of substance for sensory com- 

 munication between various parts of the cell body; and 

 these doubtless enable the cilia to act in unison, to stop or 

 start or reverse their movements with promptness and 

 efficiency. Therefore, the speed and precision of its loco- 

 motions and the promptness and extent of its responses to 

 stimulation are vastly better than in amoeba. 



