214 



THE BIOLOGY OF STENTOR 



Fig. 6i. Large fusion masses of S. coerideus. 



A. Graft of 12 stentors, heads removed, indicating bas-relief 

 sculpturing or partial emergence of constituent body shapes. 



B. Graft of 14 stentors, regenerated, showing unusually long 

 garlands of membranelles without formation of mouthparts. 



C. 1 5-mass, now organized into a bipolar system and with oral 



valency reduced to seven. (After Tartar, 1954.) 



significance from the consideration that the limit to size of regenera- 

 tion is simply that complete animals cannot be made of very few 

 parts of invariant size, but there may w^ell be a maximum organiza- 

 tion mass beyond which anything like the typical stentor form 

 cannot be realized. 



Although they do not organize into single giants, larger masses 

 show a tendency towards unification in the reduction of their oral 

 valency, number of primordia formed decreasing greatly with the 

 number of individuals grafted. A 1 5-mass for example produced 

 only 7 primordia, and a 5 5-mass had between 5 and 10 anlagen in 

 successive reorganizations. These great reductions in the number 

 of oral differentiations have yet to be adequately explained. 

 Perhaps some of the primordium sites join together as one. Or it 

 may be that in larger masses there is for some reason a competition 

 betw^een primordium sites, with fewer becoming effective in pro- 

 ducing anlagen. Partly responsible, too, may be the fact that oral 

 differentiation favors the upper surface ; for these large masses did 

 not wheel about through the water but remained on the bottom 

 always with the same side uppermost. 



