CREATION BY EVOLUTION 



The single living cells from which higher life started were 

 for a long time independent creatures, capable of assimila- 

 tion, growth, and subdivision. After a time, when the daugh- 

 ter cells adhered together, a more or less spherical colonial 

 type appeared, finally attaining regional subdivision and divi- 

 sion of labor. Then one side of the sphere grew faster and 

 a pushed-in ball appeared. Hereafter the inner layer served 

 for the digestion of the food and became the primitive gut, 

 while the outer layer not only held the bag together but 

 developed sensory and contractile powers, as in the lower 

 jellyfishes. Meanwhile the puckered skin around the mouth 

 grew out into feelers and stinging tentacles. All this looks 

 simple, but the organization of each individual cell was an 

 affair of unimaginable complexity. 



Certain jellyfishes began to give up their free-swimming 

 habits and to squirm or crawl on the muddy bottom. Pres- 

 ently the diffut;e "nerve net" throughout the body began to 

 be drawn together into definite tracts, the squirming move- 

 ments finally became more prominent in one direction, and 

 locomotion in a head-and-tail direction was already begun. 



The Origin of the Vertebrates 



The vertebrate animals originated millions of years later, 

 and there is as yet no general agreement as to what group 

 of invertebrates gave rise to the vertebrates. Professor E. B. 

 Wilson teaches that the vertebrates (or chordates) belong to 

 that great branch of the animal kingdom in which the meso- 

 derm, or middle layer of the three primary cell-layers, arises 

 from outpockets from the primitive gut, as it does also in 

 the echinoderms (the starfish group )~ and that all the articu- 

 lated animals, such as arthropods (crustaceans, insects, and 

 arachnids), annelids (worms), moUusks and other groups 

 belong to a series in which the mesoderm buds off from a 



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