164 THE BIOLOGY OF HYDRA : 1961 



TABLE 9 

 Hydroxyindoleamine distribution in fractions from Hydra littoralis 



Preparation Hydroxyindoleamine concentration 



fig. per ml. of preparation ^g. per gram dry 



tissue 



Whole Hydra homogenate 2.56 52 



Hi/dra culture medium— before 



shock 0.011 57 



Hydra culture medium— after 



shock 0.27 534 



Conditions for the shock experiment similar to those used for experiment shown 

 in Table 4. 



were made to determine if the amine was serotonin. We have dem- 

 onstrated a 5-hydroxyindoleamine by paper chromotography but 

 as yet have not been able to obtain a sufficiently clean extract 

 to determine precisely the identity of the compound. We do have 

 indirect evidence that the compound is serotonin rather than bufo- 

 tenine. This evidence consists of partition coefficients between ether 

 and an alkaline aqueous phase. A 5-hydroxytryptophan decar- 

 boxylase is present in Hydra but this only shows that the animal can 

 synthesize serotonin, not that serotonin is there. We are inclined to 

 believe that serotonin is present in Hydra littoralis, but direct proof 

 is still lacking. 



CONCLUDING STATEMENTS 



This study represents but a start toward the elucidation of the 

 chemical composition of the nematocyst. It will be of interest not 

 only to further characterize such preparations as the ones we 

 have studied, but also to separate and compare the various types 

 of nematocysts present in hydra, as well as the components of each 

 nematocyst type. This information, coupled with the excellent 

 morphology studies that are being carried out in various labora- 

 tories, could form the basis for an understanding of the manner in 

 which these intriguing organoids develop and function. 



