FACILITATION IN SEA ANEMONES. IV. THE QUICK RESPONSE OF CALLIACTIS PARASITICA AT HIGH TEMPERATURES

Preceding papers of this series have dealt with the effects of a number of treatments on the quick responses of the sea anemones Calliactis parasitica and Metridium senile. Pantin's (1935) analysis of the quick closing response in these animals showed that it is not normally elicited by single electrical stimuli, nor by stimuli following each other at intervals greater than about 3 sec. To get the closing response electrical stimuli must be given within a definite frequency range, at intervals of from about 0-2—2-5 sec- a * r o o m temperatures. Between these limits, the closer the stimuli the bigger the response, with responses occurring, of course, only to the second and subsequent stimuli. This remarkable example of a facilitated response in which the response can only occur when facilitation has been set up, and in which the amount of facilitation determines the size of the response, raised many interesting problems. My work has centred on the approach of trying to set up experimental conditions in which single stimuli are effective, as this seemed a promising way of finding out more about the nature of this kind of facilitation. Few of the treatments employed so far have caused either Metridium or Calliacti