182 THE BIOLOGY OF HYDRA : 1961 



from their nematocysts by electrical stimulation, on Carcinus mae- 

 nas, Uca ptigilator and several species of cockroaches. A brief 

 resume of some of the experiments and tentative results follows: 



1) The minimum lethal dose of a homogenate of Hydra ameri- 

 cana, in terms of the number of Hydra injected is between 5 and 10 

 Hydra for Carcinus weighing 20-30 gms.; 2-3 Hydra for Uca weigh- 

 ing 4-5 gms.; and about 5 Hydra for female Bryostria sp. (cock- 

 roach) weighing 4-5 gms. These are doses that usually kill in from 

 1 to 24 hours. The average dry weight of Hydra amcricaua, reared 

 in the laboratory, is about 35 [xg. If the paralyzing factor constitutes 

 something like 0.1% of the total dry weight, it appears that 0.2-0.4 

 fig. of toxic substance is lethal for a 20-30 gm. green crab. 



2) Heating a Hydra homogenate for 30 min. at 100 "^ results in 

 complete or nearly complete loss of paralyzing action. 



3) Electrical stimulation of numbers of Hydra (200-300) in a 

 minimum volume of distilled water discharges many of the nema- 

 tocysts. Injection of a small volume (0.05 ml.) of the fluid sur- 

 rounding the Hydra into Uca, produces symptoms that are quali- 

 tatively like those seen when whole Hydra homogenate is injected. 



4) Hydra, and Mctridiiim acontia, have been homogenized in 

 1.0% tetraethylammonium chloride (TEA). When volumes are in- 

 jected known to contain minimum lethal doses of Hydra or acon- 

 tia, none of the characteristic symptoms develop and most test 

 animals survive indefinitely. This agrees with earlier observations 

 on the autotomy reflex in brachyurans when it was found that 

 TEA very effectively antagonized the effects of coelenterate ex- 

 tracts (25). If the TEA is blocking the action of a toxic protein 

 component, and not tetramine only, this may provide a clue to 

 the mode of action of the toxin. 



REFERENCES 



1. AcKERMAN, D., 1927. tjber die IdentiUit des Atkinins mit dcm 7-Butyrobetaine. 



Zeitschr. f. Biologie, 86: 199-202. 



2. AcKERMAN, D., 1953. Uber das Vorkommeu von Homarin, Trisonellin und einer 



neuen Base Anemonin in der Anthozoa Ancmonio sulcata. Zeitschr. f. 

 physiol. Chemie, 295: 1-9. 



3. AcKERMAN, D., 1954. Richtigstellung: "Zoo-Anemonin" statt Anemonin. Zeitschr. 



f. physiol. Chemie, 296: 286. 



