12 evolution: 



ing in their construction, but if we conceive that the 

 present condition of living things is the result of con- 

 tinued modifications of the parent forms, then the 

 whole chain of life becomes intelligible to us. 



Unity of Substance. 



We have seen that all animal and plant life is 

 allied in form, and we find further that it is identical 

 in substance. The microscope discovers that the 

 vegetable cells and the animal cells are alike com- 

 posed of what is called protoplasm, or first form, 

 which closely resembles the white of ^%g, a clear 

 semi-fluid substance. One of the lowest forms of 

 animal life, the Amoeba, is just a speck of this sub- 

 stance, and in the nettle-hair the protoplasm is seen 

 lining the woody matter that forms the wall of the 

 cells that compose its structure. These cells of pro- 

 toplasm increase by division, multiplying themselves 

 and combining into varied structures. Microscopic 

 examination shows that the human body, in all its 

 parts, is built up of these little cells of protoplasm 

 The blood carries these little specks, resembling the 

 amoeba, to the place where they are to combine in 

 the structure. 



Not only is the body composed of protoplasm, but 

 it originates in a single cell of this substance, and the 

 germs which produce men, dogs, sheep, or any of 

 the highest class of animals, cannot be discovered to 

 differ by any test of microscope or chemistry. 



