BEHAVIOR 17 



Staining. Pellicle and myonemes are digested slowly. Cilia are often 

 the last to be digested and are first attacked at their distal ends, 

 then gradually disintegrating and swelHng towards the base. Gelei 

 stated that pigment granules are not digested, and certainly the 

 last stage of the food vacuole is a bright spot of concentrated pig- 

 ment; yet the fading of stentors during regeneration and starvation 

 may imply, as Weisz (1949a) maintained, that the animals are able 

 to assimilate their own coloring matter. Cannibals doubtless 

 receive advantages from their prey as food. However massive these 

 meals may be and however easily most of the substance of their 

 like may be assimilated, giant forms do not result, as in the case of 

 Blepharisma (Giese, 1938) and Stylonychia (Giese and Alden, 

 1938). Regulation of size in Stentor is therefore such as to prevent 

 gigantism or the production of forms two or more times the 

 maximum normal size. 



2. Swimming 



That ciliates rotate when swimming and describe a spiral path 

 through the water was first formulated by Jennings (1899) who 

 pointed out that such movement serves the same purpose as in 

 projectiles: by rotating, an asymmetrical body can maintain an 

 over-all straightness in the direction of its course (Fig. 2A). 

 Rotation is always predominately in one direction in a given 

 species. Jennings (1899, 1902; Jennings and Jamieson, 1902) found 

 that S. roeseli and coendeus, like most ciliates, including Parame- 

 cium, rotate to the left, i.e., front end of the animal rotates clock- 

 wise. Slightly curved toward the oral side, stentors also tend to 

 swerve in this direction so their course is a spiral. Bullington 

 (1925), who has made the most extensive studies of swimming in 

 ciliates, confirmed that three unnamed species of Stentor rotate 

 and spiral to the left. On the basis of his surveys Bullington 

 remarks that Stentor is with Coleps the only genus of more than 

 one species in which all members spiral in the same direction. 

 {Paramecium calkinsi for example rotates to the right.) This 

 generalization may be valid, for I found that the new species 

 introversus rotates to the left, as does coeruleus, polymorphus and 

 roeseli. When backing up coeruleus continues to rotate to the left, 

 as Jennings earlier noted for polymorphus. 



