36 EVOLUTION 



cattle, sheep, horses and dogs are descended 

 from a single stock or from several aboriginal 

 stocks. . . . This could be effected by the 

 future geologist only by his discovering in 

 a fossil state numerous intermediate grada- 

 tions; and such success is improbable in the 

 highest degree.' 



OTHER PAL^EONTOLOGICAL EVIDENCES. 

 There is a sublime suggestiveness in the broad 

 fact that in successive periods of the earth's 

 history higher and higher animals appear. 

 Fishes make their appearance in the Silurian, 

 Amphibians in the Carboniferous, Repliles 

 in the Permian, and Birds in the Jurassic. 

 The record as regards plants is perhaps more 

 striking in some of its details than in its 

 broad outlines (see Dr. Scott's volume in this 

 series on 'The Evolution of Plants"), but 

 every one will allow that there were Crypto- 

 gams before there were Phanerogams, and 

 Cycads and Conifers before there were any 

 ordinary Flowering Plants. 



There are other sets of suggestive facts to 

 which reference might be made if space per- 

 mitted : there is the absence of sudden breaks 

 or cataclysms; there is gradual waxing and 

 waning of races; there is the remarkable 

 phenomenon of what may be called the 

 adolescence and senescence of genera, if not 

 even species; there is the occurrence of old- 



