124 '^"^ BIOLOGY OF STENTOR 



dium grows to a greater length, extending far forward, and so the 

 size of the regenerated feeding organelles is the same and 

 proportionate. 



Of special interest is the finding of Morgan (1901b) that frag- 

 ments whose parts are rendered disproportionate by the cutting 

 do not wait, as conceivably they might, for gradual differential 

 growth to right the imbalance but adjust to proportionality 

 relatively soon. Morgan cut unfed coeruleus in two transversely and 

 observed in the anterior fragments that the stalk which was at first 

 too short then gradually lengthened, while the original membran- 

 ellar band, initially too large, became reduced to half its starting 

 size without formation of a new one, and proportionality of parts 

 was regained (Fig. 30). In posterior fragments the stalk was at 

 first too long, but it gradually came to assume normal proportions 

 and the regenerated feeding organelles were of course of smaller 

 and proper size. Reviewing his own studies, Morgan (1901b) then 

 added the statement that the regenerated organelles on the 

 posterior fragment are in fact too small and that they "later 

 become larger until the characteristic form is reached". This 

 would imply an improbable growth in situ, a question which will 

 be dealt with shortly. 



Prowazek (1904) said that he confirmed Morgan's original 

 findings and noted that they imply, with reference to the anterior 

 fragment, that there should be an imperceptible resorption of 

 portions of the old membranellar band to make it proportionate 

 in size. Such adjustment he thought was exhibited in a dramatic 

 way in the case of a stentor which divided unequally, producing 

 a smaller than normal proter which carried the now much too 

 large original ingestive structure. The feeding organelles then 

 gradually regressed until they appeared to be completely resorbed 

 while a new primordium was forming to produce a head of proper 

 proportions. Yet this behavior may be regarded as anomalous 

 because it does not occur even in the most abbreviated anterior 

 fragments in which there is more occasion for it. 



Even in normal division the original head, which is passed on to 

 the anterior daughter, is at first too large but on separation both the 

 proter and the opisthe seem to have feeding organelles which are 

 equal in size and proportionate. According to Weisz (1951b), 

 adjustment occurs in the presumptive proter during the last stages 



