66 ORGANISMS OF ONE CELL 



solid proteid matter, or in the light without solid food where it 

 manufactures its food. An allied form Astasia lives solely on 

 solids. The structures and life history of Euglena place it un- 

 mistakably with the animal flagellates. 



It is now known that plants, like animals, renew their proto- 

 plasm with oxygen, salts and proteids and give off CO 2 and other 

 waste matters the same as animals do, the only essential differ- 

 ence being their power to manufacture the proteids to be used 

 as food. Their functions, therefore, are fundamentally con- 

 structive while animals are destructive and all of their tissues 

 and organs are differentiated to subserve this great function 

 while those of animals are mainly differentiated for the pro- 

 curing of food, digesting and assimilating it. The two great 

 lines of living things have thus developed in different directions 

 and the higher we go in either scale the more easily we are able 

 to distinguish by these structural differences between animals 

 and plants. 



Spontaneous Generation. "But expectation is permissible 

 where belief is not; and if it were given me to look beyond the 

 abyss of geologically recorded time to the still more remote 

 period when the earth was passing through physical and chemical 

 conditions which it can no more see again than a man can recall 

 his infancy, I should expect to be a witness of the evolution of 

 living protoplasm from non-living matter." (Huxley, Bio- 

 genesis and Abiogenesis, p. 256.) 



All biologists are practically agreed that living matter origi- 

 nated on the earth's surface from salts and other inorganic 

 matter at a time when conditions of temperature, atmosphere 

 and other physical characteristics of the globe were very differ- 

 ent from the conditions today. At the present time, while 

 ignorant of the first causes all are agreed that living matter 

 cannot arise spontaneously from non-living and that all plants 

 and all animals come from the germs of their ancestors. All 

 theories to the contrary have been based upon ignorance, and 

 the gradual clearing away of these dark clouds forms an inter- 

 esting chapter in modern biology. A characteristic of the 

 human mind is to explain what cannot be seen or comprehended, 



