EVIDENCE FROM COMPARATIVE ANATOMY 55 



the type might be admitted, without conceding the 

 possibility of deriving one type from another. 



In reply, attention must be called to the fact that 

 comparative anatomy deals only with the animal 

 world as it now exists and that is demonstrably but 

 a very small part of the countless horde of animal 

 forms that formerly inhabited the earth, but have 

 become extinct. An oft-used illustration of the re- 

 lations between living and extinct organisms is that 

 of a great tree buried in the earth, so that only the 

 outermost twigs are exposed to view. Such twigs 

 would form scattered groups, more or less widely 

 separated from one another, the branches which con- 

 nect them being buried out of sight. If it were 

 possible to dig away the earth and expose the whole 

 tree, the continuity of all its ramifications would be 

 fully revealed. To a certain extent, this excavation 

 is accomplished by the science of palaeontology, 

 which deals with the remains of extinct animals and 

 plants as preserved in the rocks of the earth's crust. 

 Another lecture (No. IV) will be devoted to the tes- 

 timony of this science to the evolutionary hypothesis. 

 Another illustration may be drawn from a study of 

 modern languages, as it would be if that study were 

 deprived of the help given by books and manuscripts, 

 which register past changes, and confined to an ex- 

 amination of the spoken tongues. This examina- 

 tion would suffice to make clear the interrelationships 

 of most European languages; French, Italian, Por- 

 tuguese, Spanish, etc., the Romance languages, are 



