CHAPTER THREE. 



OFFSPRING OF THE SIMPLEST ORGANISMS. 



Before we can form any idea of the offspring of the 

 simplest organisms and of the way they come into 

 existence, we must become better acquainted with the 

 organisms themselves. 



1. The Simplest Living Things; Their Structures and 

 Powers. In order to understand the nature of these lowest 

 forms of life the student must know something about what 

 the biologist calls a cell. The cell is a small unit of the 

 living stuff called protoplasm. It commonly has a wall 

 around it. Our bodies and those of all the higher plants 

 and animals are made up of millions of cells. Each unit of 

 living stuff in our bodies has a kind of life of its own, 

 somewhat as a county has its life within the state. Each 

 cell lives its own life, takes up its own food, grows, divides, 

 grows old, and may die. To be sure this is not the whole 

 story. Beside doing its own private work, it does some 

 things in relation with the other cells of the body of which 

 it is a part. It does special work, as secreting or absorbing 

 or contracting or feeling, for the other cells. It has two 

 lives, so to speak: its own individual life, and its part of the 

 life of the whole organism. 



Now the simplest animals and plants are something like 

 one of these single, microscopic cells if it were turned 

 loose in nature to live an independent life. These 

 organisms are single cells. They are mostly very minute, 

 though they vary greatly in size. They must have, and 



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