THE STORY OF THE BACTERIA. 3 



cells, observe the things they do, and definitely 

 trace out their life-history. 



Cells are little masses of matter of peculiar 

 chemical constitution, and of varied shape and 

 consistence, which at some time exhibit that 

 complex of phenomena which we call life : and 

 the life of one of the higher animals is simply 

 the sum of the more or less independent but 

 co-ordinated lives of the cells which compose 

 it, all acting in harmony. 



Living things differ from the non-living in 

 that they have certain activities through which 

 their life is expressed. In the first place, they 

 are capable, in spite of various opposing forces, 

 of maintaining their individuality, and by 

 holding a balance between waste on the one 

 hand and assimilation on the other, a series of 

 capacities arise which we call nutrition, growth, 

 and development. Living things, in the sec- 

 ond place, possess certain activities by means 

 of which they are capable of producing new 

 individuals like themselves in other words, 

 they are endowed with the power of reproduc- 

 tion. Lastly, living bodies, in response to 

 varied influences, are capable of doing certain 



