THE EVOLUTION OF MAN 



of its development always shows a perceptible 

 tadpole or fish stage. Its neck shows the marks 

 of the gills and the characteristic intervals be- 

 tween them by which the fish breathing in water 

 permits it to circulate freely and flow around the 

 breathing surfaces of the gills. Furthermore, 

 the limbs which the embryos are just forming at 

 this stage have likewise the plain outlines of fins. 

 They push outward in the shape of round disks, 

 and it is only the subsequent development which 

 results in their further transformation, that is to 

 say, into actual fins here, into the swift lower leg 

 of 'a horse with a single toe there, or finally into 

 the wings of a bird or the flying hand of a bat. 

 If any strict scientific proof were still needed for 

 our claim that all these higher vertebrates con- 

 verge into a common archetype, it is obviously 

 given everywhere by this common heritage of a 

 gill and fin embryo, either in the egg or in the 

 mother's womb. The gills and fins show that the 

 oldest archetype, with which we are now dealing, 

 was represented by a gill and fin animal in other 

 words, by a fish. 



There still remains this question to be an- 

 swered: How is it with human beings in this 

 respect? Every text-book on anatomy to-day 

 gives a satisfactory answer. The embryo of 



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