ANALYSIS OF STENTOR 257 



vacuoles they grew slowly or even decreased in size. But they 

 could form primordia in reorganizations apparently induced by 

 the irradiation, or in regenerations following transection. The 

 nuclei were likewise apparently unaffected. At least some digestion 

 evidently occurred, because starvation controls decreased in size 

 much more rapidly than the irradiated stentors. Therefore, 

 Kimball concluded that X-rays inhibit growth by decreasing or 

 blocking the net synthesis from feeding, though not preventing 

 such synthesis as occurs in the building of primordia. Delayed 

 fission would hence be due to the animal's failing to attain fission 

 size or only slowly achieving the maximum volume, and not to 

 incapacity to form primordia or undergo the nuclear changes 

 which accompany division. 



These effects were independent of the presence or absence of 

 oxygen during irradiation. But anoxia combined with X-ray 

 (irradiation in an atmosphere of nitrogen) resulted in deformities 

 such as ridges, flanges, in-pocketings, and extra tails and sets of 

 feeding organelles. It seems likely that these abnormalities resulted 

 from breaks in the ectoplasm followed by improper healing; for 

 the forms described resemble those obtained by disarranging the 

 ectoplasmic pattern mechanically so that disjunctive areas no 

 longer coordinate (see Figs. 65B and 66e). If so, it may be suggested 

 that in these operations the separated areas join but fail to achieve 

 intimate union because of misorientation, while in the radiation 

 studies the orientation is at first correct, but intimate rejoining, 

 say, of the fibrous structures of the clear stripes, is inhibited as an 

 after-effect of irradiation. This in itself would be an interesting 

 effect, though still leaving the question why outgrowth and 

 joinings of fibers, which undoubtedly occurs during oral 

 primordium development, is not also inhibited. 



14. Effect of temperature on size 



A statistical sudy of variation in dimensions with temperature 

 (Zingher and Fisikow% 1931) showed that mean size of stentors 

 increases with rising temperatures up to a certain limit. Natural 

 collections accordingly showed a similar enlargement, and also an 

 increased coefficient of variation, from winter to summer. Since 

 the measurement curves were unimodal, apparently only one race 

 of coeruleus occurred in the pond sampled. Nor was illumination a 



