HELEN D. PARK 371 



the total disappears, this could be due to so many factors that I 

 wouldn't even want to speculate. 



FULTON: I have had Carolina Hydra for about a year, and as far 

 as I know it is a strain of //. Uttoralis. Like the Looniis strain this 

 Hydra becomes sexual following the surface/volume ratio experi- 

 ments. That is to say, if you take the Carolina Hydra and put it in 

 a beaker and in a flat Petri dish (I did just the two extremes), it 

 will eventually become sexual in the beaker but not in the Petri 

 dish. The only thing is that it takes about a month. It's fairly 

 slow, but it does do it. 



PARK: It is possible, of course, that the Carolina Hydra I received 

 are different from those Dr. Fulton received more than a year 

 earlier. Well, these are extremely interesting observations. Someday 

 I hope we will be able to fit our observations with those of Dr. 

 Fulton and Dr. Loomis. 



LOOMIS: About seven years ago I asked Helen Forrest what made 

 hydra turn sexual. She answered that they seem to turn sexual in the 

 laboratory whenever they turned sexual in the neighboring ponds. 

 Now this, of course, seems silly, but if one is using Versene-treated 

 tap water, then it isn't as silly as all that. Tap water from a lake 

 varies in pCOo and other factors from one season to the next. It is 

 an interesting loophole in otherwise controlled experiments. It can 

 be surmounted of course by using BVC solution made from de- 

 ionized water. A Barnstead "red cap ' mixed resin cartridge removes 

 all COo from tap water, which is not true of the standard cartridge. 



LYTLE: This is both a comment and a plea. In the interest- 

 ing report presented by Dr. Park, we have seen and heard evi- 

 dence of the existence of physiological differences among different 

 strains of a single morphological species of Hydra. I have recently 

 become concerned about this matter of subspecific differences in 

 hydroids since we now have evidence that such differences exist in 

 Hydra Uttoralis, Chlorohydra viridissima, Cordylophora lacustris, 

 and Craspedacusta sotverbii. No doubt in the next few years we will 

 see similar differences in many more species of hydroids. I have 

 just learned from Dr. Fulton at this symposium that he has observed 

 a number of rather striking differences among several strains of 



