CHAP. XVII The Evidences of Evolution 277 



never seen. Conviction depends on more than intelligence, 

 often on emotional vested interests. 



{b) Morphological. — There are said to be over a million 

 species of living animals, about half of them insects. 

 Even their number might suggest blood-relationship, but our 

 recognition of this becomes clear when we see that species 

 is often united to species, genus to genus, and even class 

 to class, by connecting links. The fact that we can make 

 at least a plausible genealogical tree of animals, arranging 

 them in series along the lines of hypothetical pedigree, is 

 also suggestive. 



Throughout long series, structures fundamentally the 

 same appear with varied form and function ; the same bones 

 and muscles are twisted into a variety of shapes. Why this 

 adherence to type if animals are independent of one 

 another ? How necessary it is if all are branches of one 

 tree. 



By rudimentary organs also the same conclusion is 

 suggested. What mean the unused gill-clefts of reptiles, 

 birds, and mammals, unless the ancestors of these classes 

 were fish-like ; what mean the teeth of very young whale- 

 bone whales, of an embryonic parrot and turtle, unless they 

 are vestiges of those which their ancestors possessed ? There 

 are similar vestigial structures among most animals. In 

 man alone there are about seventy little things which might 

 be termed rudimentary ; his body is a museum of relics. We 

 are familiar with unsounded or rudimentary letters in many 

 words ; we do not sound the " o " in leopard nor the " 1 " 

 in alms, but from these rudimentary letters we read the 

 history of the words. 



(c) Historical. — Every one recognises that animals have 

 not always been as they now are ; we have only to dig to 

 be convinced that the fauna of the earth has had a history. 

 But it does not follow that the succession of fauna after 

 fauna, age after age, has been a progressive development. 

 What evidence is there of this ? 



In the first place, there is the general fact that fishes 

 appear before amphibians, and these before reptiles, and 

 these before birds, and that the same correspondence 



