CHAPTER V. 



PAST HISTORY OF ANIMALS. 



(PaL/EONTOLOGY. ) 



One of the great interests of the study of Morphology is the 

 light that is thrown by it upon the evolution of the living 

 world. We learn, as yet only in the most general way, how 

 the various types are related to each other, and through what 

 steps they have passed before their present form was arrived 

 at. The study of form by itself must in time have led to 

 the doctrine of evolution, and from morphology many con- 

 clusions as to the course of evolution have been drawn. 

 These are checked by the study of the development of 

 individual types, for each individual recapitulates to some 

 extent in its own life-history the evolution of the race. But 

 a more satisfactory check would be that furnished by a study 

 of the races of living beings, which actually preceded those 

 that now surround us. These creatures have left various 

 traces of their existence, such as footprints, casts, and often 

 actual portions of their bodies. As opponents of the 

 theory of evolution have challenged its supporters to bring 

 forward traces of former life which should clearly prove that 

 there have been links between one type and another, it 

 has to be confessed that the collection of such links is 

 very imperfect. We must seek for reasons which shall explain 

 this. 



Reasons for the '■'■Imperfection of the Geological Record." — 

 In the first place, we must remember the great limits there 

 are to the possibility of any animal, or even of traces of any 

 animal, being preserved. Suppose we take those living 

 upon the land or in the air. How many of all these will 

 die and leave their remains in any given area ? Of those 



