No. 3] MORPHOLOGY OF THE S TEN TORS. 485 



SO pronounced in the posterior part of the animal at the 

 moment of extension that they completely underlie the granu- 

 lar stripes, as Stein has beautifully shown in one of his figures 

 of 6". roeselii. This would be impossible if the myonemes 

 were bound firmly in place beneath the clear stripes. Biitschli 

 ('89, p. 1298) has represented the myoneme of 5. ccsruleiis as 

 lodged in a "canal," lying in the " alveolarschicht " beneath 

 the clear stripe. Although I have searched for it repeatedly, 

 I have been unable to find the least evidence of such a 

 structure, either in optical or actual sections. 



Pigment. — Three distinct pigmentary substances are present 

 in the Stentors: a blue pigment in S. cceruleus and 6". multi- 

 formis, a brown pigment in 6". niger and 5. igneus nigricans, 

 and a purple-red pigment in 5. igneiis. The pigment is, for 

 the most part, lodged in the ectoplasm, and restricted (at least 

 wherever its position can be accurately determined) to the 

 granular stripes. It is thus placed in a position to receive the 

 greatest amount of light. 



The pigment of 5. ccBriilens is certainly one of the most 

 remarkable of animal pigments. Under normal conditions it 

 varies in tone from bright sky-blue to pale sea-green, and even 

 to a dull bluish-gray. When individuals are kept in unfavor- 

 able environment, as under a cover-glass, the pigment becomes 

 reduced in quantity, and changes to a yellowish-brown color; 

 sometimes Stentors are almost wholly devoid of it, and appear 

 nearly pure white. Schuberg ('90, p. 221) noted that the loss 

 of pigment took place by excretion, and I have frequently 

 observed the same fact. In a culture where Stentors are 

 undergoing depigmentation, numerous bluish-gray clots are 

 invariably found, composed largely of pigment granules. Schu- 

 berg often observed pigment in the excrement vacuole, and 

 appears to be of the opinion that it is excreted in the same 

 manner as the faecal matter. I have frequently seen such 

 pigment-containing vacuoles, but do not feel sure but that the 

 pigment they hold often belongs to a small Stentor that has 

 been swallowed as food. Furthermore, many of the clots of 

 pigment in a culture may be due to the death and disintegra- 

 tion of the feebler members of the colony. But by starting a 



