336 THE BIOLOGY OF STENTOR 



may be a different species, as Penard (1922) first suggested, and 

 as such may deserve his designation, S. gallinulus. Further study 

 is required.) 



S. amethystinus Leidy 1880. A medium-sized stentor distin- 

 guished by its violet-blue color and the fact that it does not stretch 

 out but remains habitually pyriform or conical. Macronucleus is 

 oval — hence the only medium sized blue stentor with a compact 

 nucleus. Symbiotic chlorellae are present and with the pigmenta- 

 tion often produce a dark colored animal. 



S. introversus Tartar 1958. A medium-sized (280 ^u) blue-green 

 stentor distinguished by a retractable head. When withdrawn the 

 feeding organelles and frontal field are surrounded by a lip of 

 folded lateral body ectoplasm. Endoplasm is brown, combining 

 with the pigment to give an olive-green color by transmitted Hght. 

 Monihform macronucleus. The holdfast is relatively large. 



The following species are yellow in color: 



S. niger (Miiller) Ehrenberg 1838. A medium-sized (200/x), 

 yellow to brownish stentor with an oval macronucleus. (Maier 

 (1903) states that this species has myonemes which are weaker 

 (narrower?) and that therefore the structure of the kinetics is 

 more easily studied. These animals do appear delicate as they 

 wheel slowly through the water.) 



S. felici Villeneuve-Brachon 1940. A medium-sized yellow 

 stentor with moniliform macronucleus. (According to its author 

 the yellow color of this species is not due to the granules but 

 resides in the cytoplasm. I think this is to be questioned, since in 

 all other self-pigmented species the granules are pigmented, and 

 she remarked that the color is deepest in the granular stripes. 

 S. niger at first appears to be colored throughout the ectoplasm but 

 it is the granules which are yellow.) 



The following species are small and pink in color: 

 S. igneus Ehrenberg 1838. This is a tiny (loo/x) pmk to nearly 

 colorless stentor with an oval macronucleus. It may have chlorellae 

 (Balbiani, 1893; Johnson, 1893), but all those I have seen were 

 without symbionts. According to Johnson there is no oral pouch. 

 As in other tiny stentors, the pigment stripes are few and relatively 

 broad. 



