GREAT STEPS IN ORGANIC EVOLUTION 835 



LIFE OF THE CARBONIFEROUS PERIOD.— It would be a great 

 scientific delight if we could shut our eyes and see with the inner 

 eye the appearance of the earth and its inhabitants in one geological 

 period after another. What a magnificent film it would make, with 

 the changing stage seon after aeon through millions of years, and on 

 the stage the likewise changing plants and animals vividly portrayed. 

 How dramatic it would be to see the intrusion of Ice Ages not only 

 in the Pleistocene, but over and again as far back as the Cambrian, 

 and worst of aU in the Permo-Carboniferous. How impressive to 

 follow the retreat of the fauna before the great glaciers, and to 

 witness the inexorable elimination by the way. How thrilling it 

 would be to study on the film the other Ages of Horror, the desolating 

 times of drought and aridity, when animals trekked before the 

 encroaching desert. 



On such a film the Carboniferous Period would furnish many 

 picturesque scenes, such as vast stretches of low-lying luxuriant 

 forests of quickly growing spore-bearing trees, and in these forests 

 many insects, spiders, snails, and the like, besides Amphibians great 

 and small. Sharks seem to have ruled the seas. 



In the later part of the Carboniferous Period the coal-measures 

 were laid down in humid low-ground forests; and the climate 

 throughout most of the period was mild and damp. There were no 

 dry seasons, or cold winters, and the conditions favoured luxuriant 

 vegetation and abundance of insect life. It is said that the fossil 

 trees of the period show nothing corresponding to the annual rings 

 of coniferous or phanerogamic trees, for these are due to the differ- 

 ence between the growth of the wood in the earlier and the later 

 summer months and its annual arrest in the resting season. There 

 seems to have been much stagnant water, which teemed with the 

 aquatic larvae of insects and with amphibians large and smaU. 

 Often in all probability the conditions were mild and easygoing; yet 

 did not the coal then formed make our steam age possible ? 



The coal-making forests consisted largely of graceful trees dis- 

 tantly related to our Horsetails, but sometimes reaching a height 

 of a hundred feet. Along with these were giant club-mosses and tree- 

 ferns, and some of our coal shows that there must often have been 

 great showers of spores like the "sulphur showers" of poUen which 

 are often swept by the wind from the pine forests of modem times. 

 But the Carboniferous flora included much more than Cryptogams; 

 there was a great luxuriance of seed-bearing plants of fern-like 

 habit (the "Seed-Ferns", Pteridosperms or Cycadofilices),and there 

 were lofty large-leaved trees, called Cordaiteae, intermediate between 

 the primitive maiden-hair trees (Gingko) and the Conifers we are 

 familiar with. Perhaps the "Seed-Ferns" gave rise to the Cycads, 

 which are sparsely represented in warm countries to-day, but once 

 formed great forests; and perhaps the Cordaiteae gave rise to our 



