THE CELL THEORY 3 



independent waves, instead of regarding the waves as a 

 partial interference with an underlying continuity. 



The cell theory in its original and crude form regarded an 

 organism as composed of a horde of discrete units which 

 co-operate for a common purpose and are modified in 

 various ways to make that co-operation more effective, 

 much as a human community consists of many separate 

 individuals, having different occupations and co-operating 

 for their common good. According to this idea the individu- 

 ality of any organism arose from an integration of the in- 

 dividualities of its separate cells, and is thus a corporate 

 individuality such as may exist in a school or a regiment. 

 Nowadays, however, opinion tends in the opposite direction 

 to regard the organism as the individual, with a common 

 life running through it all, and the cells not as units of 

 which it is built up but rather as parts into which it is 

 divided in order to provide for the necessary division of 

 labour involved in so complex a process as life. The con- 

 ception of the cell thus remains, but no longer requires or 

 is capable of the strict definition that was needed when the 

 word was supposed to represent a fundamental biological 

 entity. Organisms may be non-cellular if they are not 

 divided up into cells; portions of organisms may exist 

 which are not strictly cells in the old sense of the word (for 

 example Mammalian red blood-corpuscles) and yet have so 

 much the character of cells that the term may well be applied 

 to them. The word, in fact, may conveniently remain as a 

 useful descriptive term, implying as a rule a portion of 

 protoplasm containing a nucleus in immediate physiological 

 connection with it, but from which either the nucleus or 

 perhaps even the surrounding protoplasm may sometimes 

 be absent. 



Although the theory of the independence and individu- 



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