MULTICELLULAR ORGANISMS 



ization the pattern of structure of the entire colony. 

 This is an important new characteristic. 



In the colony it is still a question of viewpoint as to 

 which is to be regarded as the individual; the con- 

 stituent cells, or the entire colony. In the true multi- 

 cellular organism, (metazoa) however, the individual 

 must certainly be recognized as the entire association of 

 cells, which are now so closely integrated that they can 

 no longer be regarded merely as associated individuals. 

 Specialization and interdependence now have devel- 

 oped to such an extent that the cells of the organism 

 are incapable of individual existence outside of the 

 integrated entity. Asexual reproduction alone can no 

 longer assure perpetuation, as complexity of structure 

 has developed to such an extent as to make necessary a 

 fusion method of lowering somatic mutation damage. 

 But conjugation of entire organisms would be mechan- 

 ically awkward, to say the least, especially in the more 

 complex multicellular organisms. Consequently as 

 foreshadowed by the practice of the cell colonies, and 

 furthermore consistent with the increasing cellular 

 specialization, certain cells of the organism are desig- 

 nated exclusively to serve to propagate the species by 

 undergoing fusion with homologous cells of other 

 organisms of the species. (Or sometimes of the same 

 organism.) 



Such cells, specially designated for this purpose, are 

 known as the genetic cells. In these cells the protein 



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