EXTENSIONS OF DARWINISM ;J03 



even true insects, the latter having already become specialised 

 into several of our existing orders. All these occur either in 

 the Coal formation of Europe or the Devonian rocks of North 

 America, which seems to imply that when land-vegetation first 

 began to cover the earth a very long period elapsed before any 

 correspondingly abundant animal life was develo])ed ; and this 

 W'as what we, should expect, because it would be necessary for 

 the former to become thoroughly established and developed 

 into a sufficient variety of forms well adapted to all the dif- 

 ferent conditions of soil and climate, in order that they might 

 be able to resist the attacks of the larger plant-feeding animals, 

 as well as the myriads of insects when these appeared. So 

 far as we can judge, the vegetable kingdom was left to develop 

 freely during the enormous series of ages comprised in the 

 Devonian, Carboniferous, and Permian formations, to which 

 we must add the gap between the latter and the Triassic — the 

 first of the Secondary formations. By that time the whole 

 earth had probably become more or less forest-clad, but with 

 vegetation of a Ioav type mostly allied to our ferns and horse- 

 tails, with some of the earliest ancestral forms of pines and 

 cycads. 



In the succeeding Secondary era the same general type of 

 vegetation prevailed till near its close ; but it was then every- 

 where subject to the attacks of large plant-devouring reptiles, 

 and under this new environment it must necessarilv have 

 started on new lines of evolution tending towards those higher 

 flowering plants which, throughout the Tertiary period, be- 

 came the dominant type of vegetation. It seems probable that 

 throughout the ages animal and vegetable life acted and re- 

 acted on each other. The earliest luxuriant land-vegetation, 

 that which formed the great coal-fields of the earth, was 

 probably adapted to the physical environment alone, almost 

 uninfluenced by the scanty animal life. Then reptiles and 

 mammals were differentiated ; but the former increased more 

 rapidly, being perhaps better fitted to live upon the early vege- 

 tation and to survive in the heavy carbonated atmosphere. This 



