SEARS CROWELL 311 



REFERENCES 



1. Berrill, N. J. 1949. The polymorphic transformations of Ohelia. Quart. J. Micr. 

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3. Crowell, S. 1953. The regression-replacement cycle of hydranths of Obelia 



and Campanularia. Physiol. Zool. 26: 319-327. 



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and temperature in the colonial hydroid Campanularia. J. Exp. Zool. 134: 

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8. Crowell, S., and C. Wyttenbach. 1957. Factors affecting terminal growth in 



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Hydrozoen. I Teil: Die Hydroiden. Ergeb. Forschr. Zool. 4: 1-284. 



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DISCUSSION 



FULTON: I am much impressed with the similarity of the 

 growth pattern of Campanularia and Cordijlophora. For example, 

 if you starve Cordt/lophora, the stolon is the least affected part. 



CROWELL: We didn't say anything about longevity. Cordijlop- 

 Jiora hydranths don't die after a week or so as do calyptoblast hy- 

 dranths. 



FULTON: As far as I know Cordijlophora hydranths never die. 



STREHLER: I would like to speak on that point. We have studied 

 Bouganvillia hydranths for as long as 25 days and haven't seen 

 a single individual die. They continued to increase in size as they 

 got older. On the other hand the oldest Campanularia that we've 



