CHAPTER VII 



THE SINGLE-CELLED ANIMAL BODY. PRO- 

 TOPLASM AND THE CELL 



The single-celled body. The study of Amoeba and 

 Paramcecium has made us acquainted with an animal body 

 very different from that of the toad or the crayfish. These 

 extraordinarily minute animals have a body so simple in 

 its composition, compared with the toad's, that if the 

 toad's body be taken for the type of the animal body, 

 Amoeba might readily be thought not to be an animal at 

 all. The body of Amoeba is not composed of organs, each 

 with a particular function or work to perform. Whatever 

 an Amoeba does is done, we may say, with its whole body. 

 But as we learn the things that this formless viscid speck 

 of matter does, we see that it is truly an animal ; that it 

 really does those things which we have learned are the 

 necessary life-processes of an animal. Amoeba takes up 

 and digests food composed of organic particles; it has the 

 power of motion ; it knows when its body comes in con- 

 tact with some external object, that is, it can feel or has 

 the power of sensation. Amoeba takes in oxygen and 

 gives out carbonic acid gas, and it can produce new in- 

 dividuals like itself, that is, it has the power of reproduc- 

 tion. But for the performance of these various life-pro- 

 cesses or functions it has no 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, 



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