LAND LIFE BEGINS 43 



no other large animals on it, and was becoming rich 

 in insect food. As these lung-fishes lived more and 

 more on land, walking on their fins, the broad paddle 

 of the fin was slowly converted into a strong and 

 flexible bony stem — the leg. These ancestral quad- 

 rupeds had at first two pairs of fins, as some fishes 

 have to-day. The two pairs of fins gradually became 

 legs, with five toes (made out of five rays of the fin) 

 at the end. The lungs continued to improve. The 

 amphibian — father of our frogs and newts — made his 

 appearance. The quadruped race was born. 



Let us glance again at the vegetation. I have said 

 that there was no cold or winter anywhere on the 

 earth. We know this because the fossil plants we 

 find are all of a semi-tropical character. As there 

 was thus no winter chill, the plants throve luxuriously, 

 from pole to pole, all the year round. The whole 

 earth was semi-tropical in temperature, and most of 

 it was very damp, low-lying, steamy. This suits 

 ferns and mosses, and they, as I said, grew to gigantic 

 sizes. It suited them also that the air was rich in 

 carbon, and with all these favourable conditions the 

 plants of the time grew denser and denser. This 

 period of "perpetual summer " lasted millions of years, 

 and we are not surprised to learn that before the close 

 of it the earth was covered with such forests as have 

 never been seen since. 



Here another interesting question has been answered 

 by the story of evolution. By the beginning of the 



