21 8 THE BIOLOGY OF ST ENTOR 



through them. Invariably there was a shedding of pigment 

 granules into the interior and these clumps of blue-green debris 

 circulated around continuously in an orderly manner by action of 

 the cihary lining (Fig. 62D). There was no evidence of oral cilia or 

 of mouthparts differentiation. Several vacuoles could be present 

 together in one mass, and individual vesicles sometimes increased 

 in size as if growing and subjecting the mass to great tension as 

 indicated by the spherical form assumed. After attaining consider- 

 able size the vacuoles often broke through the surface and their 

 ectoplasm became continuous with that of the outside, giving the 

 appearance of '' ears" because of their depth and folds (e). 



In this evagination, as in their origin, the ciliated vacuoles 

 strikingly recall the unusual mode of cytodifferentiation in 

 Cyathodinium as described by Lucas (1932). During normal 

 reorganization and division in this ciliate one or two ciliary anlagen 

 arise internally, develop cilia projecting into the vacuolar space, 

 then evaginate to the outside in orderly manner so as to produce a 

 new ciliation at a different axis for the reorganized animal or the 

 two daughter cells (Fig. 62F). In both Cyathodinium and Stentor, 

 development of internal ciliation quite separate from contact with 

 the ectoplasm poses a test of the hypothesis of the genetic con- 

 tinuity of kinetosomes. But whether the basal bodies of the cilia 

 arise de novo^ or develop from division products of the surface 

 kinetosomes wandering into the interior, would be difficult to 

 decide. 



It is also possible that tubes and vacuoles may have arisen from 

 bits of ectoplasm thrust into the interior during the process of 

 grafting stentors. In several instances (unpublished) when I tucked 

 pieces of ectoplasm inside the cell, tubes and ciliated vacuoles 

 resulted. This observation is especially interesting as suggesting 

 that internal ectoplasm can grow and even undergo an orderly 

 disposition into tubes and spheres. Growth, naturally, would be 

 from the morphologically inner surface of such pieces. Cannibalized 

 stentors, though not at first enclosed in food vacuoles, are digested 

 instead, since their " growth surface " never contacts the endo- 

 plasm of the predator. And conversely, ciliated vesicles can persist 

 and develop because they are " turned inside out ". 



In a special case, tube and vacuole formation seemed to have 

 combined in a most unusual mass which showed a structure 



