44 THE INVISIBLE WORLD 



into molecules. These molecules form the nebula 

 a vast body of gaseous matter. 



Now, during the further Evolution of the nebula 

 into the solar system, there comes a time when the 

 atoms so unite in molecules as to form air, water 

 and minerals. Finally the atoms so unite in mole- 

 cules, more than a thousand in each, as to 

 form the first speck of protoplasm. It is the first 

 microbe, the first form of organic life on the earth. 



It matters not whether one, a few, or vast num- 

 bers are at first produced; they generate so 

 rapidly that, in any event, they soon spread over 

 the earth. By the processes of natural selection 

 and the survival of the fittest they finally differ- 

 entiate into varieties, species, genera, families and 

 classes, much as they exist on the earth to-day. 



