332 THE BIOLOGY OF HYDRA : 1961 



or eliminated, few hydranths are formed, and few friistules are pro- 

 duced. At intermediate rates a large proportion of the food materials 

 are utilized in hydranth budding and in medusa budding. Frustule 

 production is still low. At high feeding rates the largest portion of 

 the food materials is utilized in the formation of frustules and pro- 

 portionally less goes into the production of new hydranths and 

 medusa buds. Therefore these experiments provide some physio- 

 logical basis for the observed interactions between these three bud- 

 ding processes and suggest that these three morphogenetic proc- 

 esses are, at least in a sense, antagonistic, involving alternate 

 pathways for the utilization of metabolic su1:>strates. My present 

 hypothesis is that hydranth budding, frustule budding, and medusa 

 budding represent alternate morphogenetic pathways, and that the 

 control of budding in this system may depend upon physiological 

 competition for specific metabolic substrates. 



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