OBJECTIONS TO THE THEORY OF DESCENT. 331 



forms of life tend to supplant the old and unimproved 

 forms. 



By the theory of natural selection all living species 

 have been connected with the parent-species of each 

 genus, by differences not greater than we see between the 

 natural and domestic varieties of the same species at the 

 present day ; and these parent-species, now generally ex- 

 tinct, have in their turn been similarly connected with 

 more ancient forms ; and so on backward, always con- 

 verging to the common ancestor of each great class. So 

 that the number of intermediate and transitional links, 

 between all living and extinct species, must have been 

 inconceivably great. But assuredly, if this theory be 

 true, such have lived upon the earth. 



PLENTY OF TIME FOR THE NECESSARY GRADATIONS. 



Independently of our not finding fossil re- 

 mains of such infinitely numerous connecting 

 links, it may be objected that time can not have sufficed 

 for so great an amount of organic change, all changes 

 having been effected slowly. It is hardly possible for me 

 to recall to the reader who is not a practical geologist 

 the facts leading the mind feebly to comprehend the lapse 

 of time. He who can read Sir Charles Lyell's grand 

 work on the " Principles of Geology," which the future 

 historian will recognize as having produced a revolution 

 in natural science, and yet does not admit how vast have 

 been the past periods of time, may at once close this 

 volume. 



p When geologists look at large and compli- 



cated phenomena, and then at the figures 

 representing several million years, the two produce a 



