PROTOZOA. 155 



CHAPTER XIII. 



PROTOZOA (7TpWT09, FIRST, OV, ANIMAL) . 



THE members of this subkingdom are the lowest in the 

 scale of animal organization, their bodies consisting of 

 a soft gelatinous and structureless mass, which has a 

 remarkable tendency to form little cavities or vacuoles 

 in its substance, and is called saf 'code (crapi;, flesh). 

 They exhibit no organs, unless the cilia and certain 

 variable processes formed of the common substance 

 of the body, and which form their agents of locomo- 

 tion, be considered as such, this substance exercising 

 the combined functions of motion, sensation, and se- 

 cretion, for which separate organs exist in the higher 

 animals. 



EHIZOP'ODA (pi&, root, 7701)9, foot). The animals 

 belonging to this class consist of the structureless 

 colourless substance to which reference has been 

 made as sarcode, and they exhibit no organs. The 

 sarcodic body is slowly contractile, and portions of 

 it can be protruded at will in the form of irregular 

 root-like processes, acting both as legs for locomotion 

 and as tentacles by which the animal grasps its prey, 

 which is then forced into the substance of the body, 

 where it becomes surrounded by the surface, and a 

 cavity is formed, within which it is digested. 



Amcsba difflluens (PI. XI. fig. 10) is common in 

 water in which portions of plants have been kept for 

 some time. When first placed on the slide, the body' 

 appears as a minute, transparent, rounded mass of 

 jelly -, but if observed for some time, it will be seen 



