368 0. C. Glaser and C. M. Sparrow 



It is not necessary to give a detailed analysis of the experiments 

 summarized in Table I. In general they indicate that specific 

 chemical effects are not involved, and further that any theory 

 which attempts to explain the discharge of nematocysts, must take 

 account of the nematocyte. This particular phase of the subject, 

 how^ever, can be more profitably discussed after the experiments 

 on isolated nematocysts have been reported. These also will 

 explain some of the above results which at first sight may appear 

 puzzling. 



EXPERIMENTS WITH ISOLATED NEMATOCYSTS 



A nematocyst is a membranous capsule, one portion of which 

 is prolonged into a thread, ending in a point. In its undischarged 

 state, this thread is introverted, and is stored inside the capsule 

 of which it is an organic part. In addition to the visible filament, 

 the capsule contains certain invisible chemical substances. 



On the basis of this knowledge, we may make certain assump- 

 tions regarding the causes that bring about eversion of the thread, 

 and these assumed causes can then be tested experirrtentally. 

 We may assume that in order to bring about discharge, it is neces- 

 sary to raise the internal pressure of the capsule to a point at which 

 it can overcome the effect due to the uniform external pressure to 

 which the capsule is subject, plus whatever resistance to eversion 

 is offered by the construction of the capsule itself. We may as- 

 sume further, that the capsule is a membrane, semi-permeable to 

 aqueous solutions, and that it contains substances capable of 

 absorbing water. We may assume also that the membrane is 

 specifically permeable to certain ions, although, if the results of 

 the experiments can be explained without this assumption, postu- 

 lation of specific permeability becomes unnecessary. 



These assumptions were tested experimentally. The results 

 which have been actually obtained appear to be explicable by 

 any one, or any probable combination, of the following factors : 

 increase of internal pressure; decrease of external pressure; reduc- 

 tion in the resistance to eversion due to the construction of the 

 capsule. 



