AMCEBA, PARAMCECIUM AND VORTICELLA 45 



special parts or organs, no mouth or alimentary canal, no 

 lungs or gills, no legs, no special reproductive organs. We 

 have here to do with one of the "simplest animals." With a 

 minute, organless, soft speck of viscous matter called pro- 

 toplasm for a body, the simplest structural condition to be 

 found among living beings, Amceba nevertheless is capable 

 of performing in the simplest way in which they may be 

 performed, those processes which are essential to animal 

 life. 



Paramecium has a body a httle less simple than Amoeba. 

 The food-particles are taken into the body always at a cer- 

 tain spot; this might be spoken of as a mouth. And the 

 body has some special locomotory organs, if they may be so 

 called, in the presence of the cilia. The body, too, has a 

 definite shape or form. But, as in Amoeba, there is no 

 alimentary canal, nor nervous system, nor respiratory sys- 

 tem, nor reproductive system. The whole body feels and 

 breathes and takes part in reproduction. 



A long jump has been made from the toad and crayfish 

 to Amoeba and Paramoecium; from the complex to the 

 simplest animals. But, as will later be seen, the great 

 difference between the bodies of these simplest animals and 

 those of the highly complex ones is only a difference of 

 degree; there are animals of all grades and stages of struc- 

 tural condition connecting the simplest with the most com- 

 plex. When animals are studied systematically, as it is 

 called, we begin with the simplest and proceed from them 

 to the slightly complex, from these to the more complex, and 

 finally to the most complex. There are hundreds of thou- 

 sands of different kinds of animals, and they represent all 

 the degrees of complexity which lie between the extremes 

 we have so far studied. 



The cell. — The characteristic thing about the body of 

 Amoeba and Paramoecium and the other "simplest animals" 

 — for there are many members of the group of "simjilest 



