44 THE BIOLOGY OF STENTOR 



animals is often seen to be thrown into transverse waves or convo- 

 lutions. Therefore, the granular stripes appear to be merely fill-ins 

 where surface granules come to occupy spaces left between the 

 structured clear bands and membranelles. Accordingly, it is the 

 granular and not the clear stripes which should have been called 

 mere " between-stripes " (" Zwischenstreifen ") even though they 

 are more obvious to the eye. Moxon, for instance, found that in 

 crushed coeruleus the pigment stripes disperse while the clear 

 bands persist as refractile structures, and Schroder remarked the 

 same. The great change in width of the former speaks for the same 

 conclusion, contrasting with the uniformity of the clear stripes. 

 When the area of ectoplasm in coeruleus is greatly reduced, the 

 patch remaining stretches to cover the whole and this stretching 

 occurs mainly in the pigmented stripes which become very broad 

 (Fig. 9a). Furthermore, where stripe increase occurs it can be seen 

 that the pigmented bands adapt in width and contour to the 

 exigencies of the situation (Fig. 9B), which would not be the case 

 if they had to maintain a uniform and stable structure. 



These stripes are characterized by uniform, spheroid inclusions 

 about ijLt in diameter. They are not fixed in place but capable of a 

 certain freedom of movement (Andrews, 1946) which Weisz 

 (1949a) called Brownian motion. In all colored species the 

 pigmentation is probably confined to these granules (though 

 S. Felici was differently described), for there is not a second set 

 of uncolored bodies. That cortical granules seem to be present in 

 uncolored stentors indicates that they serve some purpose besides 

 pigmentation. When pigmented, some granules can also be identi- 

 fied in the interior of the cell ; and Weisz indicated this to be the 

 main site of a putative metabolic function, the granules being 

 stored, as it were, in the ectoplasm and loosed into the interior to 

 be utilized during starvation and regeneration. Within the interior 

 of coeruleus, Andrews (1955) reported that the pigment granules 

 move between the endoplasmic vesicles as if gliding along films, 

 by a movement not yet explained. 



Granules can also be cast off to the exterior by the action of 

 mild irritants (see p. 250). This effect resembles the discharge of 

 trichocysts, which are, however, always spindle-form. Hence 

 the granules have been called protrichocysts by Prowazek (1904), 

 Kahl (1935), and Faure-Fremiet et al. (1956). 



