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LIBBIE H. HYMAN 



parts of both. In terms of metabolism, the metaboUc rate de- 

 creases from the head of the anterior zooid backwards, rises at 

 the head of the second zooid, falls again, and finally rises steadily 

 to the posterior end. Figure 10 illustrates a stage in the disinte- 



J:y-,,^^ 



Fig. 10 A stage in the diaintegration of a Dero with a well developed posterior 

 zooid. 



gration of the two zooids, and figure 11 is the corresponding 

 graph. As the development of the head of the posterior zooid 

 proceeds, its susceptibility to cyanide continually increases, ap- 

 proaches that of the head of the first zooid, and eventually exceeds 

 it. Meantime, processes of reorganization have been going on 



