i6 



and younger trees stretching far out, developed from seeds 

 carried by the wind. 



Insects apparently went out on land about the same time as the 

 plants, but before backboned creatures were living out of the 

 water almost a hundred million years more passed, and that is a 

 very long time. 



In those early days there was apparently abundant life in 

 most of the waters, but the vertebrate fishes such as the Crossop- 

 terygii appear to have lived mainly in fresh-water swamps. Now, 

 fish need oxygen just as we do, but they get theirs from the water, 

 which dissolves a little from the air. If water loses its oxygen, 

 fish cannot live in it, and we have all seen what happens when 

 dams and vleis start to dry up. Rotting vegetation in water uses 

 up all the dissolved oxygen, and you find fish dying and dead all 

 round the margins of such bodies of water. For the same reason 

 one putrefying fish will kill many others. 



There have apparently always been floods and droughts for 

 long or short periods. In a short sudden drought there would be 

 heavy mortality of swamp fish. In a slow drought fish would not 

 be killed off^ so quickly, and it is apparent that sometimes in those 

 early days, fishes gasping in putrefying pools, managed to live by 

 absorbing a certain amount of oxygen directly through surface 

 blood-vessels, probably in the mouth and gill cavity. Over long 

 ages certain types probably learnt to gulp air and to breathe at 

 least partly that way, first by necessity, then by choice. This 

 would have tremendous consequences. First of all, when a drought 

 came and pools began to dry up, such fishes could live long enough 

 in air to flop out and perhaps reach other and better water, and so 

 survive. Over long ages fishes doing this probably came to spend 

 more and more time out of the water, possibly in getting from one 

 pool to the other they found succulent food on the way. Gradually 

 some fishes gave rise to creatures more suited than themselves to 

 life on land, creatures that could live on land and in water, the 

 so-called amphibians, of which the modern frog is an example. 

 Fins began to modify and change to limbs, and so was taken this 

 greatest step in the history of life as it affects us, the first real 

 step that led to man. 



This is where the Coelacanth comes into the picture. There 

 were two main lines in the Crossopterygii, named Coelacanths 



