4O C. M. CHILD. 



the distinct boundary between disintegrated and intact regions 

 at all times and the uniformity with which the change advances 

 at all points of the circumference of the body. Occasionally, 

 however, modifications of the process appear. In a small 

 percentage of the animals used for the experiment, not more than 

 one or two per cent., the advance of disintegration ceases for a 

 time when it has reached about the stage represented in Fig. 3, 

 i. e., when about the oral half is disintegrated. Then after one 

 or two minutes the disintegration of the aboral half occurs- 

 almost simultaneously in all parts. In one individual observed 

 (Fig. 6) the disintegration of the oral half occurred in the usual- 

 manner, then there was a pause of about one minute and then 

 the disintegration of the aboral half began from the aboral end. 

 Fig. 6 shows this individual a few seconds before disintegration 

 was complete. A narrow band of intact body wall on which 

 the cilia were seen to be still moving separates the two areas of 

 disintegration. During the next few seconds the aboral area 

 advanced over this band and completed the process. This is 

 the only case among thousands observed in which disintegration 

 proceeded from the aboral end instead of toward it. 



The length of life in the reagent before disintegration begins 

 and the rate of advance of disintegration over the body vary 

 within wide limits according to water-temperature, concentration 

 of the reagent and alkalinity, but the course of the process is the 

 same in all cases with the rare modifications described above. 



Another species of Stentor, apparently 5. polymorphous, gives 

 the same results, but the course of disintegration is not so readily 

 followed in this species because of the absence of pigment and 

 the less conspicuous myonemes. 



III. HYPOTRICHA. 



Several species of hypotrichous ciliates including two species 

 of Stylonychia, Euplotes and two unidentified forms have thus 

 far been tested by this method and with the same result in all 

 cases, viz., death and disintegration begin at the anterior end 

 and proceed down over the body to the posterior end. When the 

 animals are placed in KCN they at once begin to swim backward 

 and continue to do so until death and disintegration occur. 



