362 0. C. Glaser and C. M. Sparrow 



strong" solutions of sugar or salt. Here too the nematocysts were 

 not discharged, but when the preparations were subsequently 

 washed out with distilled water, the nematocysts exploded. Gros- 

 venor also experimented with the tentacles of actinians. When 

 these were plucked off, and quickly thrust into a 50 per cent solu- 

 tion of sugar, and teased into small fragments, though many dis- 

 charged nematocysts were found, pieces in which none had dis- 

 charged were common enough. Such fragments were isolated 

 and kept for from 24 to 72 hours. The nematocysts remained 

 undischarged until the sugar solution was washed out with water, 

 when approximately 20 per cent of the capsules discharged them- 

 selves. 



"These facts," says Grosvenor, "seem to show that the dis- 

 charge of nematocysts is due to osmosis. The capsule apparently 

 contains a solution of such strength that it takes up water from 

 such a weak solution as sea w^ater, but not from the protoplasm of 

 the nematocytes, or the fluids in the alimentary canal of iEolids, 

 or from any of the other solutions mentioned above." 



Our interest in the history of the nematocysts of yEolids, ('02; 06) 

 led us in the summer of 1908, to undertake a careful investigation 

 of this subject. The work was begun by the Senior author in 

 the Zoological Laboratory of the University of Michigan, and 

 was brought to a practical completion in the Marine Biological 

 Laboratory at Woods Hole. To the Director, Prof. F. R. Lillie, 

 we are indebted for the use of a room in the laboratory. 



MATERIAL AND METHODS 



The material used for the experiments and for the development 

 of methods consisted of Hydra, Metridium, Physalia, and Mon- 

 tagua. Experiments were made with the nematocyst bearing 

 tissues of these animals, and also with the isolated stinging cap- 

 sules. The methods used for isolating them were peptic and 

 auto-digestion at 35° C, and maceration in sea-water to which 

 crystals of chloretone had been added. In the case of the peptic 

 digestions, all the tissues except the nematocysts, were dissolved 

 in a solution composed of 4 cc. HCl; 1000 cc. H2O Dist.; and 



