DEGENERATION. 17 



natural selection of the fittest, led to the production, 

 from shapeless primitive living matter, of all the 

 endless varieties of complicated plants and animals 

 which now people the world. Countless varieties 

 have died out, leaving only their modified de- 

 scendants to puzzle the ingenuity of the biologist. 



Of the tens and hundreds of thousands of interme- 

 diate forms we know nothing by direct observation. 

 They have perished as better fitted forms ousted 

 them in the never-ending conflict. But we feel sure 

 that they once were in existence, and can infer what 

 was their structure, and what were their peculiarities, 

 by the study of the structure and attributes of their 

 now living descendants. 



If all the forms of life at present living are the modi- 

 fied offspring of a smaller number of ancestral forms 

 which have died out, and if these again were the modi- 

 fied descendants produced by ordinary parentage of 

 a single original living thing — then the whole series of 

 forms that have ^2^^r lived could, if we had them before 

 us, be arranged in the form of a great family-tree — 

 the various branches presenting a perfect gradation of 

 forms arranged one after another, leading down from 

 the terminal twigs (which would represent the latest 



C 



