The Physiology of JSIematocysts 38 1 



3 The explosive pressure varies with the individual nemato- 

 cysts, and w^ith circumstances. It may be artificially altered. 

 This fact explains why the nematocysts of iEolids explode in sea- 

 water, whereas those of Coelenterates do not unless the nemato- 

 cyte is stimulated. 



4 It is impossible to show that the nematocyte is a factor in 

 the discharge of the nematocysts of Coelenterates under all circum- 

 stances. Nevertheless, this is true under some circumstances, 

 and perhaps always under the conditions which are normal in the 

 lives of cnidaria. 



5 The osmotic theory, originally advanced by Grosvenor on 

 very limited evidence, is absolutely supported, as far as isolated 

 nematocysts are concerned, and may be applied to the normal dis- 

 charge of stinging capsules in Coelenterates, if we suppose that 

 stimulation of the nematocyte inaugurates changes which result 

 in the liberation of heat or in lowering the concentration of the 

 intra-cellular medium immediately surrounding the nematocyst. 

 Both heat and dilution may be operative. 



6 The filaments of nematocysts are capable of penetrating 

 the tissues of other animals, contrary to the opinion of Mobius, 

 but in order to do this, must make iheir punctures before eversion 

 is complete. 



Zoological Laboratory 



University of Michigan 



November 25, 1908 



