180 THE BIOLOGY OF HYDRA : 1961 



(see refs. 13, 22, 23, 25, for summaries of this and other earHer 

 work ) . 



II. Quarternary ammonimii compomids: 



Several nitrogenous bases have been isolated from various coe- 



lenterates, including the following: „ . 



° ° References 



tetramethyl ammonium hydroxide or "tetramine" 4, 11, 17, 27 



N-methylpyridinium hydroxide 5 



homarine 2, 10, 17, 27 



trigonelline 2, 27 



y-butyrobetaine 1, 27 



zoo-anemonin 3, 6, 27 



Of these bases, the only one that has marked paralyzing action 

 is tetramine (4, 27). It is the only one fomid thus far in a fresh- 

 water coelenterate (27). It is a known toxic component of certain 

 molluscan tissues (7, 9). With the exception of zoo-anemonin, the 

 other bases listed above are widely distributed among marine 

 invertebrates where they may play a role in osmoregulation ( 10, 27 ) . 



III. 5-Hydroxytryptamine (serotonin, 5-HT) : 



This very potent pain-producer and histamine releaser has now 

 been identified in a variety of coelenterates (17, 25, 26). It is pres- 

 ent in the coelenteric tissues of Calliactis parasitica in very large 

 amounts ( 17 ) but in other coelenterates it is most abundant in 

 regions (tentacles and acontia) where nematocysts are concentrated 

 (25,26). 



IV. Histamine and histamine releasers : 



Histamine has been found in some coelenterates but not in 

 others (17, 24). Potent histamine releasers have been extracted 

 from a sea anemone ( 12) and Cyanea (24) . 



V. Active proteins: 



Much evidence indicates that the paralyzing and edema-pro- 

 ducing actions of coelenterate toxins are due, in large measure, 

 to a protein component(s) (8, 13, 14, 15, 16, 21, 22, 23). There 

 is some evidence that this component acts on cholinergic neurons 



