WHY WE MUST BE EVOLUTIONISTS 



inner corner of our eye there is just a trace of what is called 

 the third eyeHd, a structure that is strongly developed and 

 readily seen in most mammals, as well as in birds and 

 reptiles. It serves to clean the front of the eye ; but although 

 it is big enough to do this in most mammals and birds it is 

 a mere relic in man. Take another example: behind the eye 

 of the skate — a familiar flat fish — there is a large hole called 

 the "spiracle." It serves for the incoming of the "breathing 

 water," which washes the gills and passes out by the live pairs 

 of gill-clefts on the under surface. But if we peer into this 

 very useful breathing-hole or spiracle we see a minute comb- 

 like structure, which is the dwindling useless relic of a gill. 

 The cleft or spiracle is of indispensable use to the skate, 

 but the relic or vestigial gill inside the spiracle is of no use 

 at all. Yet it tells us that a spiracle was evolved from a 

 gill-bearing gill-cleft. 



One of the most remarkable sets of facts about living 

 creatures — plants as well as animals — is that old structures 

 become transformed into things very new. The poet Goethe 

 helped to make the great discovery that the parts of a flower 

 — sepals, petals, stamens, and carpels — are just four whorls 

 of transfigured leaves, the stamens and carpels being spore- 

 bearing leaves. We sometimes see the whole flower of a 

 flowering plant that has become too vegetative "go back" 

 and become a tuft of green leaves; and it is an unforgettable 

 lesson to pull the flower of the white water lily to pieces and 

 to find that the green sepals pass gradually into white 

 petals, and these gradually into yellow stamens. 



Similar lessons are taught by animals. What is the sting 

 of a bee but a transformed egg-laying organ or ovipositor 

 (therefore never found in drones) , and what is an ovipositor 

 but a transformed pair of limbs? The elephant's trunk was 

 a great novelty in its way, but it is just a very long nose with 



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