Its Composite and Dissoluble Nature. 151 



cell of the colony may act as a brain or nerve cell. The 

 capacity is inherent in all cells at the outset of multi- 

 cellular life. The protozoan unicell exhibits functions of 

 muscle, brain, and gland. One cell, living alone, may do 

 all that any multicellular organism can do, on a small 

 scale. But in a colony of unicells — from which multi- 

 cellular creatures originated — and particularly in a large 

 colony, certain cells, on account of their outer or inner 

 location in the colony, come habitually to do certain things 

 and assume certain functions. Those on the outside unite 

 to propel the colony onward toward food; those on the 

 inside deal with the food after it is seized and ingested ; 

 and there come to be those which take it upon themselves 

 to spy food, or to scent it at a distance, iu a word, to act 

 as eyes, ears, and nose for the colony. 



But to convey what these cells saw, or scented, for the 

 benefit of the colony, to other cells, those for example 

 which propel the colony, it was necessary that certain 

 intermediate cells, or lines of cells, should actas carriers 

 of this intelligence and pass it on from cell to cell, and 

 here we have the origin of a nerve — a line of cells pass- 

 ing intelligence to the other cells, those which propel the 

 colony. In this necessity of the many-celled colony we 

 find the beginning of the function of nerve and, ultimately, 

 of brain. For very soon the need of a common center to 

 which the conveyed intelligence from without could be 

 brought, would make itself felt. Certain cells would be 



