CHAPTER III. 



THE ORIGIN OF THE ANIMAL KINGDOM. 



WE have now the history of life fairly started. 

 Living matter made its appearance in the geological 

 seas of the far distant ages, and was at first probably 

 an undifferentiated mass with the simplest powers of 

 assimilation and growth. Out of this the higher 

 orders of life were to arise, and we have now to study 

 the first steps toward the modern world. 



Unicellular Life. 



The first trace of anything leading toward the 

 modern world, of which we find evidence, is in the 

 formation of cells. It has been suggested in the last 

 chapter that there first existed a diffused mass of 

 living matter without differentiation into parts. 

 Such a conclusion has not been proved, and if such 

 a mass did exist, it probably continued only a short 

 time. It soon became broken up into small masses 

 which were more or less independent of each other. 

 Our reasons for this conclusion are these : The 

 simplest and lowest organisms which exist to-day 

 consist of just such little independent bits of proto- 

 plasm which we call cells (unicellular organisms). 



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