PROGRESS 17 



We know that there was a time when the earth, 

 hot and fiery, could not have been the abode of life. 

 Of the first origins of life we know nothing and 

 guess little. What we can justifiably surmise is that 

 the protoplasm of the original organisms was not 

 yet differentiated into cytoplasm and nucleus, and 

 that sexuality had not yet arisen. The bacteria, 

 however specialized in other ways, are still in this 

 primitive condition. 



Later, we can with great probability infer that 

 the independent units into which the stuff of life 

 was subdivided reached a size which, though still 

 minute, was at least not beyond or even close to 

 the limits of microscopic vision ; they were further 

 provided with a nucleus, and occasionally underwent 

 sexual fusion. In other words, they showed an organ- 

 ization which we call cellular ; they were free-living 

 cells. Such unicellular creatures must have been at 

 one epoch sole inhabitants of the earth, and diverged 

 into the most manifold types of structure and modes 

 of life. Such of them as led an animal as opposed 

 to a plant type of existence would be classified under 

 the Protozoa or unicellular animals.^ 



The colonial habit gives advantages of increased 



1 There is a certain school of biologists who object to 

 describing Protozoa as cells. This to others appears pedantic. 

 But, whether or no they are right in the matter of terminology, 

 the fact which I am here emphasizing remains, viz. : that 

 Protozoa had to be aggregated before the Metazoa, or many- 

 celled animals, could arise. 



