322 THE BIOLOGY OF STENTOR 



further, we can only note that since the mouthparts are induced by 

 the ectoplasm of the posterior pole, this induction or its gradient 

 basis is apparently highly labile in certain stocks. 



Fluorescence. That fluorescence is characteristic of certain races 

 of coeruleus was discovered by MoUer (see p. 48), these animals 

 when killed appearing red in ultraviolet radiation.* Other races lack 

 the trait, although they look the same in visible light because the 

 major component of the pigment is the same in all coeruleus and is 

 not fluorescent. Whiteley and Moller (unpublished) neatly demon- 

 strated fluorescence to be a trait under control of the nucleus. When 

 animals of a fluorescent race were enucleated, the fluorescence soon 

 disappeared; or if the macronucleus of fluorescents was replaced 

 by the nucleus of a non-fluorescent race the fluorescence still 

 disappeared. Therefore the manifestation and maintenance of this 

 trait seems to depend upon the presence of a certain type of 

 nucleus and may be regarded as a genetic characterization of great 

 interest in itself and also potentially valuable in tagging cells of 

 diflferent origin. 



Cannibalism} In the discussion of feeding reactions in stentors, 

 reference has already been made to the work of Gelei (1925) on 

 cannibalism in coeruleus. One of the main points of this study was 

 that the proclivity for eating one's fellows is a racial character. 

 This conclusion was based on the observation that some samples 

 from a culture, containing a natural collection of stentors which 

 was not a clone, showed cannibalism and others did not. Daughters 

 of cannibals cannibalized each other. Even when not densely con- 

 centrated, and regardless of whether they were well-fed or not, 

 cannibals seemed actively to pursue their fellows, while in other 

 samples the stentors simply turned away on encountering each 

 other. On dubious grounds Ivanic (1927) questioned that canni- 

 balism is a racial character in protozoa, including Stentor. More 

 to the point is my observation of cannibalism in all 9 stocks or 

 clones of coeruleus which I have under cultivation, strongly indicat- 

 ing that cannibalism is common to all representatives of this 

 species regardless of origin. 



Other possible racial differences have been indicated in respect 

 of the following characteristics: Requirement, or not, for high 



*Lately (i960) Moller reports that some races of S. coeruleus exhibit 

 all degrees of fluorescence. 



