THE LIVING WORLD. 



The first point that strikes out attention in this 

 history, is that the life of plants has been more evi- 

 dently one of progression than that of animals. We 

 do not find that the Silurian (2) age opened with an 

 abundant and highly specialized flora to correspond 

 to the highly developed fauna of the times. The 

 plants were few and all of the lower orders. Com- 

 paratively speaking, then, we may say that the ani- 

 mal kingdom had reached a much higher state of 

 development by the beginning of the Silurian than 

 the vegetable kingdom. While all of the classes of 

 animals (except two) had appeared at this time or 

 during the Silurian age, there were no plants higher 

 than rhizocarps, and nearly all of the plants in exis- 

 tence were algae or still lower types. The whole 

 vegetable world which is familiar to us to-day was 

 still to be developed. 



We notice next that although in the early periods 

 the animal world developed faster than the vegetable 

 world, still we find that before the close of the geo- 

 logical ages the relation was reversed. The vegeta- 

 ble kingdom reached its culmination long before the 

 animal kingdom. With the Cretaceous (8), the vege- 

 table world had developed its highest types, the sub- 

 sequent history being only an elaboration of them. 

 But at that time the highest class of animals had not 

 appeared at all, for the true mammals came into 

 existence only in the next age (Tertiary), and very 

 great advance took place in them even later. 



In general it remains to be noticed that with the 

 opening of the Silurian, the vegetable kingdom had 

 reached a condition where cellular differentiation was 



