ON THE PERSISTENT TYPES OF ANIMAL LIFE 93. 
amount of modification which living beings have undergone during 
geological time is but very small in relation to the whole series of 
changes which they have suffered. In fact, paleontology and physical 
geology are in perfect harmony, and coincide in indicating that all we 
know of the conditions in our world during geological time, is but the 
last term of avast and, so far as our present knowledge reaches, 
unrecorded progression. 
