198 THE HAUNTS OF LIFE 



possible seeds are to become real seeds which 

 will sprout. And even when the pollen can 

 pass from the stamens of the flower to the pistil 

 of the same flower (self-pollination), the results 

 are not usually so good as when the pollen is 

 carried by insects (or by the wind) from one 

 blossom to another. When there is cross- 

 fertilisation the yield of seeds is better. And 

 the plants so produced tend to be more variable, 

 which will be a good thing if it is useful for the 

 plant to change. 



The Third Great Invasion. It was about 

 the end of the time known as the Devonian or 

 Old Red Sandstone that amphibians made their 

 appearance, and, in the next age, the Carboni- 

 ferous, when the coal measures were laid down, 

 they had their golden age. These early amphib- 

 ians, ancestors of our frogs and toads, newts 

 and salamanders, were the advance guard of 

 the third great invasion, which eventually led 

 to the appearance of reptiles, birds, and 

 mammals. This third invasion meant the 

 opening up of many new possibilities for 

 animals, and, in the long run, it led to 

 man. 



It is interesting to notice some of the new 

 things that began with amphibians, the advance 



