368 THE CONCEPT OF EVOLUTION 



ary formulation be true. For how otherwise can we account, 

 for instance, for the twisting and moulding of the same 

 fundamental materials, notably bones and muscles, to make 

 the fore-limb of a frog, the paddle of a turtle, the wing of 

 a bird, the fore-leg of a horse, the flipper of a whale, the 

 wing of a bat, or the arm of man ? Can these homologies, 

 this ' adherence to type ' be understood save as indicating 

 blood-relationship? How can we interpret the numerous 

 useless vestigial structures in higher animals except 

 as the dwindled relics of structures which were well-de- 

 veloped and functional in ancestral forms? The two sets 

 of teeth in whalebone whales that never cut the gum, the 

 deeply buried representative of hip girdle and hind leg 

 in many Cetaceans, the hint of a third eyelid in man, are 

 they conceivable except as historical vestiges, like the un- 

 sounded letters in many words, to use Darwin's comparison, 

 or like the functionless buttons and buttonholes in our 

 clothing? What apart from evolution can be the signifi- 

 cance of the classifiability of organisms into varieties, species, 

 genera, families, orders, classes, and phyla, of the ' con- 

 necting links ' and ' synthetic types ' ? There seems no 

 alternative between a miraculous world and an evolved one 

 when we learn that the blood of a horse mingles harmoni- 

 ously with that of an ass, and a hare's with a rabbit's, while 

 man's blood added to any of them produces destruction 

 of corpuscles. Blood-relationship is not a metaphor ; its 

 degree can be measured by a precipitate. We cannot visit 

 the exhibitions of pigeons and poultry, of cats and canaries, 

 of cabbages and chrysanthemums, of roses and apples, with- 

 out asking: If Man has utilised organic variability to such 

 purpose in a short time, what may not Nature have effected 

 in the course of many millions of years ? The rock record 



