CHAPTER III 



It has already been exjDlained that the lowest organ- 

 isms arc probably quite beyond our ken. Higher or- 

 ganisms than these appear as minute aud apparently 

 formless specks, the protogenes of Haeckel, visible only 

 under the highest powers of the microscope, and com- 

 posed of that transparent jelly, "the formal basis of all 

 life," which is known as protoplasm. About them also 

 we have as yet been able to learn little beyond the fact 

 that they are living beings. Higher in the scale are 

 such organisms as the amoeba; about them we are able 

 to learn much that is important and instructive. They 

 opcupy that point in the scale of life at which the plant 

 and animal kingdoms begin to diverge the one from the 

 other, and though excessively minute, are larger than 

 the protogenes, and therefore better observable. Each 

 is a little mass of protoplasm in which may be seen a 

 dot, the nucleus, which is usually situated eccentrically, 

 and which, as modern research seems to have established, 

 is the most important part of the organism. Such a 

 speck of living protoplasm as the amoeba is known to 

 biologists as a cell ; and of such cells or variations of 

 them the structures of all plants and animals are built 

 up, a plant or animal composed of a single cell being 

 known as a unicellular organism, whereas a plant or 

 animal composed of a plurality of associated cells is 

 known as a multicellular organism. Since such uni- 

 cellular organisms as the amoeba are fairly observable, 



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