EVIDENCE FROM PALAEONTOLOGY 95 



fossiliferous rocks show that most of the principal 

 types of animal life were already differentiated at 

 the time when those rocks were formed and hence 

 there is little hope of finding the beginnings of those 

 types. It must not be forgotten that there is abun- 

 dant indirect evidence that life had existed on the 

 earth through unimaginably long ages before the 

 formation of the earliest fossiliferous rocks; that is 

 what Darwin meant when he said that the geological 

 record contained only the last volume of the world's 

 history. 



An admirable illustration of the manner in which 

 the evidence of fossils may serve to show the con- 

 nection between types which are very widely sepa- 

 rated in the modern world, is afforded by the vegeta- 

 tion of the Carboniferous period, the last but one 

 of the Palaeozoic divisions. This luxuriant vegeta- 

 tion was composed almost entirely of non-flowering 

 or cryptogamic plants and, in addition to a great 

 variety of ferns, giant lycopods and horse-tails, there 

 were two groups of especial interest to evolutionists: 

 (1) the Sphenophyllales, very slender, probably 

 trailing and climbing plants, which are intermediate 

 in structure between the two cryptogamic classes, 

 the lycopods and horse-tails. Doubtless, they were 

 the survivors in Carboniferous times of more ancient 

 plants which were, in turn, the common ancestors 

 of the two classes named. (2) A proverbially im- 

 passable gulf yawns between the flowering and the 

 cryptogamic plants and yet the gulf is at least par- 



