42 BIOLOGY 



complicated by the addition of other elements, and also 

 by the fact that the response may be a conscious or 

 an unconscious one. 



CHAPTER VIII 



MOTION AND LOCOMOTION 



WHILE it is quite true that every living organism ex- 

 hibits some form of motion, this does not imply that 

 it is visible to the naked eye. What is generally spoken 

 of as motion, that is, the movement from place to place, 

 is really locomotion, and as such must not be confused 

 with the former. 



Most animals are capable of moving from place to 

 place ; that is, they have the power of locomotion, and 

 this is necessary to their existence, for their food is only 

 local in distribution. Certain types, such as the zoo- 

 phytes, barnacles, &c., are fixed and more plant-like, 

 but all such forms live in a medium, the sea, where 

 food is more evenly distributed and constantly circu- 

 lated by the currents therein. On the other hand, the 

 great majority of plants are fixed, but as their food is 

 found practically everywhere, that is no disadvantage, 

 and such locomotion as is found in the higher plants is, 

 as a rule, purely physical and dependent on the absorp- 

 tion or evaporation of water. Moreover, locomotion in 

 the higher plants and also in such of the lower forms 

 as exhibit it, is not associated with the quest for food, 

 but usually with the dispersal of the offspring. 



The protoplasm within every cell, if that cell be 



