339 THE HISTORY OF CREATION. 
ment of geological periods. Our life is a single drop in 
the ocean of eternity. The reader may call to mind the 
duration of life of many trees which is more than fifty 
times as long; for example, the dragon-trees (Draczena) and 
monkey bread-fruit trees (Adansonia), whose individual life 
exceeds a period of five thousand years; and, on the other 
hand, the shortness of the individual life of many of the 
lower animals, for example, the infusoria, where the indi- 
vidual, as such, lives but a few days, or even but a few 
hours, contrasts no less strongly with human longevity. 
This comparison brings the relative nature of all measure- 
ment of time very clearly before us. If the theory of de- 
velopment be true at all, there must certainly have elapsed 
immense periods, utterly inconceivable to us, during which 
the gradual historical development of the animal and vege- 
table kingdom proceeded by the slow transformation of 
species. There is, however, not a single reason for accept- 
ing a definite limit for the length of these periods of 
development. 
A second main objection which many, and more especially 
systematic zoologists and botanists, raise against the theory 
of descent, is that no transition forms between the 
different species can be found, although according to the 
theory of descent they ought to be found in great numbers. 
This objection is partly well founded and partly not so, for 
there does exist an extraordinarily large number of tran- 
sition forms between living, as well as between extinct 
species, especially where we have an opportunity of seeing 
and comparing very numerous individuals of kindred species. 
Those careful investigators of individual species who so 
frequently raise this objection are the very persons 
