b THE BIOLOGY OF STENTOR 



Striping stop short of the posterior pole. Cross-sections of con- 

 tracted animals show a corrugated surface with the clear stripes 

 lying in valleys between the raised granular stripes. 



A thin pellicle forms the outermost surface of the cell. It could 

 conceivably be the product of secretory activity, special elaboration 

 of which may produce cyst walls and the cylindrical cases found 

 in some species. The pellicle is not completely elastic and on 

 contraction is thrown into transverse folds over the granular 

 stripes, causing the surface of the rounded animal to appear like 

 a scalloped theater curtain. 



The graded variation in the width of the granular stripes 

 provides a fundamental asymmetry to the pattern of the cell. In 

 the oral meridian these bands are narrowest and they gradually 

 increase in size around the cell from left to right so that the widest 

 bands eventually come to lie next to the narrowest in a locus of 

 stripe- width contrast on the oral or ventral side. Stripe multiplica- 

 tion occurs in this region, the widest granular stripes being split 

 by the interpolation of new clear bands. Because this splitting 

 generally proceeds from the anterior end and does not follow all 

 the way through to the posterior, there results a triangle of shorter 

 stripes which was called the ramifying zone by Schuberg (1890). 

 This area is also the region in which the oral primordium appears. 



All stentors attach by a temporary holdfast organelle at the 

 posterior end. In undisturbed cultures only a few animals will be 

 found freely swimming (Gelei, 1925), and this may be taken as the 

 usual condition in nature. 



Stentors sink to the bottom in agitated cultures, their specific 

 gravity being greater than that of water. Attachment may serve 

 the purpose of keeping them with minimum expenditure of energy 

 in favorable locations toward the surface of the water where oxygen 

 is abundant. It may also be assumed that the effectiveness of the 

 feeding vortex created by the peristome is increased when the 

 animal is attached. 



Adherence is firm. Animals just detached remain sticky at the 

 posterior end and Jennings (1902) saw them dragging trails of 

 mucoid material behind. If water is pipetted out of a culture, 

 the stentors remain fastened to the sides in a watery film. Rapid 

 evaporation may even leave animals stuck to the rim of the vessel 

 where they dry and die, seemingly unable to loose themselves. 



