294 THE BIOLOGY OF HYDRA : 1961 



CROWELL: This frequency (of three times an hour or so for hy- 

 dranth movement) surprises me, because, in the stolon anyway, if 

 one watches the movement back and forth of the fluid, one gets a 

 periodicity in the order of 3 to 5 minutes in all the hydroids I've 

 looked at. 



FULTON: Have you looked at Cordylophora? 



CROWELL: Yes. 



FULTON: In the Cordylophora stolons I've followed, there are 

 a pair of filling and emptying cycles about every twenty minutes, 

 which corresponds to the frequency at the hydranths. 



CROWELL: I don't doubt that. What you see in the hydranths, 

 I think, is different from the typical back and forth flow in the 

 stolons. 



FULTON: I don't think so, but we're still in the process of finding 

 out. 



CHAPMAN: I wonder if you have any information about tlie 

 relationship between culture conditions, such as tonicity, tempera- 

 ture, and pH, on the spacing of these uprights? 



FULTON: I have voluminous information. Actually not much 

 affects interupright spacing, but many things affect the general 

 pattern of colonies. Kinne has made a thorough study of the ef- 

 fects of different dilutions of seawater and of different tempera- 

 tures on colony pattern. I think that all it would be wise to say right 

 now is that the pattern which I get is the pattern one gets in stand- 

 ard culture solutions at 22° with one feeding a day and all the ritual. 

 One can get almost any colony shape one wants simply by varying 

 one parameter or another. So this is quite a labile system. 



LOOMIS: What strikes me in your nice growth records is a sort 

 of feeling that the stolon is trying to escape from itself. In other 

 words, it is trapped in its own one dimensional line and starts grow- 

 ing a shoot upwards. Then growth has to escape from this shoot 

 and does so first to the right and then to the left. New growth largely 

 takes place in a new axis at right angles to old growth, which is 

 another way of saying that growth can take place only at an open 



