AXIAL GRADIENT IN CILIATE INFUSORIA. 47 



the swelling always toward the center. This direction of move- 

 ment results from the distribution of the cilia and the weight of 

 the swelling. In many cases the swelling bursts sooner or later, 

 the contained cytoplasm flows out, a wave of disintegration 

 accompanied by an increase in translucency passes rapidly over 

 the remaining portions of the bcdy, toward the posterior end, 

 blotting out the ectoplasmic structure and the cilia and all that 

 remains is the mass of granules spreading in the water, the 

 meganucleus and a small transparent ectoplasmic "shadow" of 

 the portions not directly involved in the swelling (Fig. 22). 



In other cases the dissolution of structure occurs throughout 

 the body before the rupture of the membrane and the body may 

 retain the shape of Fig. 21 for some minutes but finally the 

 membrane disappears and only a shapeless granular mass con- 

 taining the meganucleus remains. 



In higher concentrations of KCN or in lower concentrations 

 with increased alkalinity disintegration is more rapid but its 

 course is essentially the same. In KCN 0.02 m. or in KCN o.ooi 

 m. which is made more alkaline by the addition of NaOH death 

 and disintegration occur within ten to fifteen minutes. The 

 course of disintegration is much the same as that described above, 

 a small swelling containing granular cytoplasm lighter in color 

 than the rest appears over the anterior vacuole, but the vacuole 

 dees not enter it in most cases (Fig. 23) ; this swelling increases 

 rapidly in size and soon involves the anterior end of the body 

 (Fig. 24) ; sooner or later its membrane disappears, the wave of 

 disintegration spreads over the body, blotting out its structure 

 and only a mass of granular protoplasm and the contracted 

 "shadow" remaining (Fig. 25). In a few individuals droplets of 

 semi-fluid hyaline substance appeared on other parts of the body 

 surface and increased in size until bursting occurred. 



In these solutions a swelling over the posterior vacuole appears 

 much more frequently than in KCN o.ooi m. without the addition 

 of alkali or even in o.oi m. In most cases where a posterior 

 swelling appears it is smaller than the anterior, but occasionally 

 it is larger and rarely only the posterior swelling appears. In 

 general, the higher the concentration of the reagent, whether 

 with or without the addition of alkali, the more frequently the 



