BIT BY BIT INVENTION : TEETH AND SCALES 309 



doubt both wholesome and agreeable, but it is not without 

 its difficulties. If the snake breaks the egg before eating 

 it, what becomes of the yolk ? If it eats the egg before 

 breaking it, what becomes of the shell ? Dasypeltis calls 

 to its aid the outstanding processes of its neck-vertebrae. 

 These were primarily intended to serve for the attachment 

 of muscles, but now they are made to change their direc- 

 tions, and to stand forward through the muscles into 

 the throat. They become tipped with enamel, like true 

 teeth. Dasypeltis swallows the egg whole, breaks it in 

 the gullet by its vertebral teeth, and when the contents 

 are swallowed, discards the shell. 



Human invention has this great advantage over what 

 we are compelled to call the invention of Nature, that it 

 can readily take short cuts. When man has once laid 

 hold of a real improvement, all the steps by which that 

 improvement was attained become a mere matter of anti- 

 quarian curiosity. When the light wheel, built up of 

 nave, spokes, and tire, has once been got, we give up 

 cutting sections of tree-trunks. But Nature goes back 

 to the beginning time after time. Stages of development, 

 long superseded, may be abbreviated or disguised, but 

 they are not quickly lost. The higher animals begin their 

 individual lives as simple cells, very like, at least super- 

 ficially, to Amcebae, or to the cells which compose the 

 colonies of the lowest Protozoa. In the further course of 

 their development they may reproduce as transitory struc- 

 tures organs which they have never actually used since the 

 time when the Silurian rocks were forming. 



Fresh organs are nearly always made by giving a new 

 shape to old ones. Hence the patient ingenuity of Nature 

 is fettered by a load of tradition, and not a few structures 

 which we perceive to be exquisitely fitted for their place 

 were originally meant for something else. The develop- 

 ment of every animal is a condensed history of adapta- 

 tions. 



