CHAPTER IV 



Multicellular Organisms 





THE CELL-COLONY AS AN INTERMEDIATE FORM 



The development of multicellular organisms from 

 the unicellular creatures marks the next integration 

 towards greater complexity in the evolution of life. 

 For a better appreciation of the nature of the develop- 

 ment of the multicellular organisms, it is helpful to 

 consider some of the forms of life which stand inter- 

 mediate between one-celled creatures and the fully 

 integrated multicelled organisms. 



Such an intermediate form of life are the cell- 

 colonies. The volvox is a rather typical example of 

 such a colony. Here one is dealing with an association 

 of cells which, while they do nQt yet constitute a clearly 

 defined multicellular organism, are certainly some- 

 thing more than just a random aggregate of cells. The 

 individual cells of such a colony, if cut loose from the 

 main body, are at times able to exist by themselves, but 

 more frequently die not very long after leaving the 



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