154 THE BIOLOGY OF HYDRA : 1961 



CAPSULE 



Until recent years the nematocyst capsule was thought to be 

 chitinous (2) With the advent of the controlled mass culture 

 technique for the cultivation of H. littoraUs (13) it became feasible 

 to grow in the laboratory the large number of animals needed for 

 chemical studies on these structures. Under most conditions em- 

 ployed to disrupt Hydra one finds that most of the nematocysts dis- 

 charge. Advantage of this phenomenon was taken by Dr. LenhofI, 

 who, by a procedure of differential centrifugation, was able to iso- 

 late nematocyst preparations, largely discharged and free of the bulk 

 of other tissue components (Table 1). When we chromatographed 



TABLE 1 

 Isolation of discharged nematocysts from Hydra 



1. Live animals disrupted in 10 kc sonic oscillator. 



2. Suspension centrifuged 15 minutes at 160 g. Supernatant recentrifuged. 



3. Whitish residues pooled and resuspended in water. 



4. Residues centrifuged 20 minutes at 200 g. 



5. Residue contained at least three types of nematocysts— penetrants, volvents, and 



glutinants — about 80% are discharged. 



hydrolysates of such a preparation we found numerous amino acids, 

 among them, one which was identified chromatographically as 

 hydroxyproline (9). This compound, to my knowledge, has never 

 been demonstrated in any protein other than collagen. The quanti- 

 tative distribution of this compoimd between the protein of the 

 whole Hydra and the nematocyst preparation shows that it is con- 

 centrated in the latter ( Table 2 ) . We have also found high amounts 

 (over 20%) of the other imino acid, proline, in the nematocyst prepa- 

 rations (10). The absolute values obtained for the imino acid con- 

 centration in nematocyst preparations have shown some variation. 

 More recent determinations of the hydroxyproline indicate that it 

 is present in even higher concentrations than shown in the above 

 table. These differences can be largely due to variations in the 

 purity of different preparations. Since, in animals, high concen- 

 trations of these imino acids have been demonstrated only in 

 collagens, we conclude that the capsule of the Hydra nematocyst 



