178 THE BIOLOGY OF HYDRA : 1961 



mal cells suggesting that there may be a migration through the 

 gastrovascular cavity? 



LANE: Yes, I've found them in gastrodermal cells, but they 

 have been in cells which have incorporated this material from 

 prey organisms. 



BURNETT: Are they in a state of digestion? 



LANE: That's right. Normally the nematocysts end at the lip of 

 the gastrozoid. The lip is always identifiable by having cnidoblasts 

 in its ectoderm, but none in its gastroderm. 



Actually, we've had a great deal of trouble in keeping these 

 animals in captivity. Probably the reason for this is that they have 

 no protection against dragging their tentacles on the bottom. When- 

 ever this happens the fragile surface epithelium is destroyed so 

 that the next time the tentacle contracts, it squirts out some of this 

 gastrovascular fluid. It's interesting that within an hour of placing 

 a mature PhysoUa in an ordinary aquarium tank, the surrounding 

 water becomes ninhydrin-positive. He loses much fluid. This is one 

 reason why we have been unable to keep these animals in captivity 

 long enough to feed them, and then study the distribution of 

 digested food materials to the gastroderm. 



LARSON What can you tell us about the pharmacological action 

 of the toxin? 



LANE: We haven't enough information on the pharmacology 

 of the toxin to justify any statements. 



GOREAU: Can rabbits be immunized against Physalia toxin? 



LANE: Yes. The material is sufficiently antigenic to develop good 

 titers. It is difficult, however, to difl^erentiate between a lethal and 

 an immunizing dose. 



GORDEAU: That's the problem of anaphylactic shock which 

 was discovered with Physalia toxin by Richet. If you could immunize 

 an animal against the toxin and label the antibodies with suitable 

 fluorescent groups it might be possible to find out whether there 

 is transfer of toxin from the gastroderm through the mesoglea into 

 the epidermal nematocyst batteries. 



LANE : Yes, that would be an interesting experiment. 



