FINE STRUCTURE 43 



pellicle to be a double or perhaps even a triple membrane, joined 

 to the body cilia because continuous with their outer walls. When 

 the pellicle is elevated the cytoplasm does not flow out into the 

 spaces provided and hence there is another film, the plasma 

 membrane, which was also shown to be double. One may regard 

 the pellicle as being a somewhat dispensable secretion of the cell 

 because salt treatments often produce the shedding of a layer which 

 is presumably the outermost, but the stentor remains intact, 

 appears not to be significantly affected, and probably re-secretes 

 the layer. These remarks are demonstrably true for Blepharisma 

 (Nadler, 1929). 



In cross-sections of contracted stentors the surface is thrown 

 into a series of ridges parallel to the longitudinal axis of the cell. 

 Each ridge represents one of the granular or pigmented stripes 

 (" Rippenstreifen " of Butschli) while the alternating valleys are 

 the clear stripes (Zwischenstreifen). The bases of the rows of body 

 ciUa are implanted along the (animal's) left side of each valley or 

 clear stripe. 



It was early noticed that on contraction the stripes of pigmented 

 or non-pigmented granules are thrown into folds, transverse 

 ridges, or crenulations while the clear stripes are not. Schroder 

 remarked that this pleating may cause the granules to be aligned 

 in rows, which indicates that these particles have some freedom 

 of displacement. Hence the original deception that these bands 

 were striated muscles. The appearance described impHes that the 

 pellicle has a limited elasticity, at least over the granular stripes, 

 and that it is more elastic or simply pinned down in the region of 

 the clear stripes. 



Presumably there is a break in the pellicle permitting extrusion 

 at the holdfast and no pellicle over the cytostome. 



(b) Granular stripes: nature of the pigment and granules 

 As already described in Chapter II, the ectoplasm is chiefly 

 characterized by alternating clear and -granular longitudinal stripes 

 or bands. In colored stentors the granules are pigmented, giving 

 the appearance of pigmented stripes. These stripes seem to be 

 without specialized structures other than the granules located in 

 them ; but the clear bands mark the site of complex differentiations, 

 including not only the ciliary rows but also a band which in living 



