THE ORIGIN OF MAN 87 



large as black bear. The ground sloths were 

 represented by a large and widely spread form, 

 while the giant southern had a body as large as 

 that of an elephant, though shorter in limb. Of 

 ruminants related to the musk-ox they occurred 

 later in the period and of the bison there were 

 at least seven kinds. 



We have thus seen how life originated and how 

 it has evolved through countless ages. We have 

 witnessed the formation of small animals from 

 inanimate inorganic matter. Animals that were 

 composed of only one cell, small microscopical 

 animals, whose period of activity, by this I mean 

 the time when they were the only form of animal 

 life on this earth, is known as the age of unicel- 

 lular life. Then came the dominancy of the trilo- 

 bites, the first invertebrate animals and which 

 were followed by the rise of shelled animals. 

 Following these came the rise of the nautilids, 

 armored fishes and corals. With the first air- 

 breathing animals, namely the scorpions, we have 



