170 DARWINISM AND THE PROBLEMS OF LIFE 



rudimentary. But we shall see later on that we cannot 

 accept this principle. 



However, there has been one result from our inquiry. 

 Although we were unable to discover the causes that 

 account for the rudimentary organs, their existence is a 

 convincing proof of the theory of evolution. We cannot 

 understand the existence of these useless organs unless 

 we suppose that they had a purpose in the ancestors of 

 their possessor, and were then fully developed ; and 

 that they had to be transmitted steadily to posterity by 

 the force of heredity. These useless appendages can 

 never be reconciled with a theory of creation. 



Still greater is the testimony to the evolution of 

 organisms of the rudimentary organs that appear and 

 disappear in the lifetime of an animal. 



We said at the beginning of this chapter that an 

 amphibian shows, in the course of its early development 

 from an aquatic to a terrestrial animal, how a salamander 

 or a frog must have evolved from a fish in past ages. 

 We find similar reproductions of its evolutionary history 

 in ancient times more or less in the embryonic develop- 

 ment of every animal. All living things descend from 

 protozoa, the microscopic beings that we find in a drop 

 of water ; and every animal begins its life at the same 

 stage, since the ovum entirely resembles one of these 

 protozoa. After the protozoa came the polyps, from 

 these the worms, and from these again the fishes. Now 

 we find in the development of every vertebrate ovum, 

 including the human, stages that may be compared with 

 those three forms. Haeckel gave the name of "the 

 biogenetic law" to this phenomenon, and attached a 



