1/8 THE LIVING WORLD. 



tree. In this comparison we have seen that the tree 

 is to be regarded as an old one, all of whose branches 

 show by their shattered condition, the effects of the 

 storms of the ages. Comparatively few branches 

 remain alive, while a larger number have either dis- 

 appeared or become reduced to a few still vigorous 

 shoots. The highest branch alone appears to be in 

 its primal vigor, still rapidly growing and expanding, 

 and this because of the influence of a new life prin- 

 ciple, perhaps engrafted into the old tree. 



Now if such a comparison is a correct one, it 

 is evident that the tree must be looked upon as 

 being near its death. Of course, however, it is pos- 

 sible to question the correctness of this comparison, 

 and we must therefore ask whether there are really 

 any grounds for believing that the life of the world 

 has passed its prime, that while man is the crowding 

 creation, his appearance indicates the decline of the 

 living world as a whole. 



Development More Rapid in Early Ages. 



In order to answer this question in the affirmative, 

 it will only be necessary to refer to some of the facts 

 already noticed regarding the previous ages. First 

 we may notice again the significant fact that the 

 development of the animal kingdom seems to have 

 been more rapid in the earliest times than it has 

 been in subsequent ages. The diversity of the Silu- 

 rian (2) fauna has already been noticed, and this, of 

 course, means that a large part of the evolution of 

 type had occurred previous to the Silurian age. All 



