AXIAL GRADIENT IX CILIATE INFUSORIA. 4! 



The process of disintegration is in all essential features similar to 

 that in Stentor and consists in a dissolution of the structure and a 

 swelling of the cytoplasm. The boundary between the disin- 

 tegrated and intact regions is sharp and the disintegrative change 

 proceeds uniformly clown the body, the rate of advance varying 

 in different individuals and with different temperatures and 

 concentrations of reagent. 



In Stylonyclria the beginning of disintegration is marked by the 

 melting down of the structures at the anterior end into a mass of 

 uniform semi-fluid cytoplasm while the cilia elsewhere are still 

 active and the animal is moving rapidly backward. The dis- 

 solution of structure extends backward over the body and the 

 disintegrated mass often stretches out and is left behind in a 

 long trail of granules and semifluid droplets as the animal moves 

 backward: Movement continues in each part until the advanc- 

 ing wave of disintegration reaches it, when it suddenly breaks 

 down and seems to dissolve into a formless mass. The pos- 

 terior end continues to move until finally it too dissolves and 

 movement ceases. 



The advance of the disintegration wave and the sudden melting 

 of each structure as the wave reaches it are striking phenomena 

 and the uniformity of the whole process in different individuals 

 and in different species indicates that it is associated with a 

 fundamental feature of the constitution of these cells. 



If the concentration of the cyanide is so low that the animals 

 live for an hour or more before disintegration begins Stylonychia 

 usually loses its flattened elongated form and becomes almost 

 spherical, but movement still continues and the anterior end is 

 still distinguishable by its structure. In such cases the dis- 

 integration, when it finally occurs, is more rapid and extends 

 from anterior to posterior end in a few seconds. 



IV. PERITRICHA. 



The forms examined include three species of Vorticellidae and 

 one of Carchesium. The results are practically identical in all 

 cases. All of these forms are more resistant than Stentor and 

 require a higher concentration of reagent. In Carchesium 

 for example the course of death and disintegration in KCN 



