CHAPTER XXXIX 

 APPEARANCE OF LIFE 



SUCCINCT as they are, these previous considerations are 

 sufficient for understanding the phenomenon of the pro- 

 gressive evolution of living organisms. 



The study of the fossil forms discovered in geological 

 strata forms quite different from those of the present 

 day shows that animals of high organization appeared at 

 comparatively recent dates. This gives us to understand 

 that these higher species have been formed by a progressive 

 accumulation of acquired characters resulting from individual 

 adaptations to conditions that varied unceasingly. If we 

 possessed the complete collection of ancestors of some pre- 

 sent-day individual, we should find in them the history of the 

 formation of its species and of all the adventures through 

 which the species passed without ever dying. For the capital 

 point of the evolutionary history of a species as much as that 

 of an individual is that the evolution has never been inter- 

 rupted by death. This enabled Darwin to assert that beings 

 of the present day are an elite, and so on back from each 

 preceding generation, since all their ancestors lived at 

 least to the age of reproduction. 



Just as the living being comes from an egg which, ana- 

 tomically, is far more simple, so species of the present come 

 from ancestral species of the past which, from every point of 

 view, may have been enormously less complicated. Thus 



