486 JOHNSON. [Vol. VIII. 



small colony and keeping a rigid census of it, it is easy to 

 ascertain that pigment is thrown out of the bodies of living 

 Stentors. As Schuberg remarks, pigment accumulates about 

 the foot of Stentors that remain long fixed in one place; it 

 is evidently thrown out by the naked protoplasm of the foot. 



The blue coloring-matter of 6". ccendeus is perhaps the most 

 indestructible of all animal pigments. Butschli observed ('89, 

 p. 1476) that neither alcohol, ether, nor chloroform dissolve it, 

 and Lankester ('73) found it unchanged by dilute acetic, hydro- 

 chloric, and sulphuric acids, while an alkali (dilute potassic 

 hydrate), "had the effect of intensifying the blue color." The 

 only reagents I have used that attack it are osmic acid and 

 platinic chloride, both of which change its color to brown. ^ 



Cilia. — The whole surface of the Stentors, in common with 

 all other Heterotricha,^ is clothed with cilia. As previously 

 stated, the cilia are inserted in rows along the clear stripes 

 (Figs. 5, 7, r/.). The narrower the granular stripes, the nearer 

 together the rows of cilia; consequently the ciliation is densest 

 in the pharyngeal funnel, where the stripes are the narrowest 

 of any on the body.^ The cilia are not of equal length on all 

 portions of the body. Those of the frontal field are shorter 

 than those of other parts; and they are somewhat longer on 

 the posterior than on the anterior regions of the body. 



The structure of the cilia does not appear to differ from that 

 of these organs among Metazoa, although I have not been able 

 to detect a "root" within the pellicula. A thickened basal 

 piece (" Fussstiick ") is, however, readily demonstrable by use 

 of osmic acid. (Fig. 7). The absence of a "root " is not to be 

 assumed because of failure to detect it; such a structure has 

 been shown to exist in nearly all cilia and ciliary structures. 



1 The only recorded effort to determine the chemical composition of this remark- 

 able substance is the spectroscopic examination made by Lankester ('73). Its 

 spectrum indicated the presence of a peculiar substance, called by Lankester 

 Stentorin. It is characterized by the presence of two strong absorption bands, 

 one in the red, the other in the green. " Stentorin is interesting as being an 

 addition to the very short list of animal substances which give banded and there- 

 fore characterizable absorption spectra." 



2 The aberrant Caenomorpha alone excepted. 



* This fact is readily demonstrated by compressing a Stentor beneath a cover- 

 glass sufficiently to cause eversion of the pharynx. 



