The Physiology of Nematocysts 373 



sure of the intracapsular fluid must be about the same. It was 

 found that at ordinary temperatures, practically all of the nemato- 

 cysts discharged in a solution of 70 per cent distilled and 30 per 

 cent sea-water, whereas practically no explosion occurred in a 

 mixture of 60 per cent sea-water and 40 per cent distilled. Since 

 this latter dilution gives yVir X 22, or 9 atmospheres as the mini- 

 mum pressure required to bring about explosion, it is easy to see 

 why a simple vacuum proved wholly inadequate. 



Heat 



Low temperatures hinder discharge, and make it necessary to 

 employ solutions of much greater dilution than are needed at 

 ordinary temperatures. High temperatures on the other hand 

 greatly facihtate discharge, and make it possible to explode nemato- 

 cysts in media more concentrated than sea-water. These effects 

 in all probability are due to a combination of factors. 



In the case of low temperatures, the capsule probably contracts, 

 and thus renders more difficult, not only the absorption of water, 

 but the actual extrusion of the thread through the narrow opening 

 out of which it must be everted. The increase in the viscosity of 

 the medium due to the lowering of the temperature is also a con- 

 siderable quantity. When dealing with high temperatures on the 

 other hand, the viscosity of the surrounding medium is reduced; 

 the expansion of the capsule not only makes absorption easier, 

 but also the actual process of eversion; further the pressure within 

 the capsules must be raised, partly on account of the increased 

 speed of the molecules in the intracapsular fluid, partly on account 

 of an actual increase in the number of molecules present, forPor- 

 tier and Richer ('02) have shown that the hypnotoxin breaks 

 down at 55° C. 



Alternating Current 



Although capable of causing the discharge of nematocysts 

 imbedded in their living mother tissues, when applied to the iso- 

 lated capsules the alternating current proved ineff'ective. The 

 result is explained by the fact that an alternating current is inca- 



