312 THE BIOLOGY OF STENTOR 



to be considered in arriving at any reliable interpretation of the 

 effects resulting from species differences in cytoplasm and nuclei. 



What may be called the capacity of foreign macronuclear nodes 

 to support oral primordium formation and development in 

 enucleated coeruleus from which the oral region was also removed 

 has received a preliminary survey. We have to say preliminary, 

 because nuclear transfers are not easy and the number of cases 

 with certain combinations is still few. That there should be many 

 is indicated both by the circumstance that one cannot always be 

 sure that the last macronuclear node of the coeruleus has been 

 removed, as well as the experience of Lorch and Danielli (1950) 

 with interspecific transfers in Amoeha in which many tests gave 

 negative results though a small percentage could produce effective 

 combinations. Hence the positive result is more significant in 

 showing what an alien combination can do ; but the negative result, 

 in which no primordium formation occurs, may be merely the 

 result of other factors such as poor viability or insufficient number 

 of cases to include possible rare instances in which the combination 

 would work. 



In the first place, controls showed that nuclei could viably be 

 transferred from one individual to another among similar stocks 

 of coeruleus leading to their subsequent complete regeneration. The 

 next closest combination was between typical coeruleus and an 

 organism I called Stentor ''X" (Tartar, 1956c). The latter was a 

 small, blue-green stentor like coeruleus but only about i/8th its 

 volume, with far fewer stripes, usually opaque cytoplasm, and tiny 

 nuclear nodes. This organism was at least a distinctly different 

 variety of coeruleus, or possibly even a different though closely 

 associated species. Transfers could be made in both directions and 

 it was found that the nucleus of either could support regeneration 

 in the cytoplasm of the other (Fig. 88). This may be called the 

 expected result, because we can assume that the nature of nuclear 

 support of regeneration is the same in all species and varieties of 

 Stentor. Size of the feeding organelles was always appropriate for 

 the host cytosome. Yet the chimeras did not survive as long as 

 controls and soon died. This is the reason it is thought that the 

 two were distant varieties, if not separate species. The appearance 

 was, therefore, that a successful interaction between nuclei and 

 cytoplasm of different type was later and gradually overwhelmed 



