DEVELOPMENT OF THE ORGANISM 



narrow neck, which has nothing to do with the neck of the 

 young child. Along the sides of the neck there are two 

 series of gill slits, and, just as in the tadpole, these become 

 covered by flaps of skin that grow back from the head and 

 join the trunk. The neck indentation is thus obliterated, and 

 the head passes without a break into the trunk, just as it does 

 in the older tadpole. The blood vessels at the sides of the 

 gill clefts resemble exactly those of the tadpole. There are 

 four of them on each side, and, with accurate imitation of 

 the tadpole, the third on each side drops out. The sala- 

 mander retains the four throughout life, but its near cousin, 

 the newt, drops out the third, as does the frog. Thus the 

 stoiy of man's development from a water animal and his 

 gradual closing up of his gill clefts is accurately repeated in 

 the womb, and the distortion of this story by the develop- 

 ment of the placenta is easily recognised. We find the same 

 history if we study the development of the young lizard 

 within its mother; but here no placenta is developed, and 

 the egg is afterward laid, but development has begun long 

 before that. So by comparing the life histories of different 

 animals belonging to the same phylum we can separate the 

 secondary accretions from the original story and thus recover 

 the true ancestral history. 



To return to human development: As this proceeds the 

 limbs grow out and the embryo comes to resemble an ordi- 

 nary four-footed animal, but the fingers and toes are at first 

 webbed like those of a frog. At this stage there is a well- 

 developed tail, and later there is a complete covering of 

 hair, resembling the hairy skin of an ape. At birth the big 

 toe is widely separated from the other toes, just as is the 

 big toe of an ape, and the legs curve inward at the ankles, 

 so that when the child is held upright only the outer edge 

 of the sole rests on the ground. This arrangement of the 



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