54 THE INVISIBLE WORLD 



thus keep the earth clean; and in thousands of 

 other kinds of work. 



Now this tendency, commenced in microbian 

 life, is continued and carried to a much higher 

 degree in multicellular life. With the microbe 

 the aim is to accomplish a single thing to make 

 alcohol, wine, beer, cider, or tear in pieces dead 

 matter. In every case the aim is simply to do one 

 thing. The workers therefore in every case are 

 one species. The work is one, the colony is one, 

 and every member of the colony helps do that one 

 work. 



But with the cell the plan in view is complex. 

 The object is to build up many parts, as the 

 parts of a plant, or the organs of the animal, 

 with these parts so related to one another as to 

 constitute a complete organism. As each part is 

 different in form and texture from every other 

 part, it requires a different kind of workers. 

 There are therefore as many different colonies, or 

 species of cells, as there are different parts in the 

 organism to be built up and sustained. Each 

 colony of cells, like the colony of microbes, is ap- 

 pointed to do a single kind of work. But each 

 colony works also with the higher aim so to do its 

 work, so to build and sustain its part, that it may 

 be harmonious with, and helpful to, all the other 

 parts of the complex organism. As an individual, 

 the cell works, like the microbe. As a colony, the 

 cell works with the higher object to make and sup- 

 port a body with parts complete. Microbes form 



