CHAPTER XIV. 

 Causes of Animal Evolution. 



(i) Animal Substance. — Although animal substance 

 differs from vegetal and mineral substance, yet this 

 difference is more structural than constitutional ; for 

 the same elements which form animals form also 

 vegetals and minerals. 



The elements which form organic substance are 

 sixteen in number, eight being non-metallics and 

 eight metallics, as follows : — oxygen, nitrogen, car- 

 bon, silicon, sulphur, phosphorus, chlorine, iodine ; 

 along with hydrogen, potassium, sodium, calcium, 

 magnesium, aluminium, iron, and manganese. Animal 

 substance is thus a dual or sexual compound. 



(2) Cells and Unicellular Animals. — The evolution 

 of an animal cell or a unicellular animal from ele- 

 mentary matter is no more difficult to natural laws 

 than the evolution of a vegetal cell or a unicellular 

 vegetal from the same or similar substance. The com- 

 ponent atoms may differ, but only slightly, while the 

 processes of evolution must be governed by the same 



