ANALYSIS OF STENTOR 247 



anterior to the posterior pole followed by a wave of ectoplasmic 

 disintegration in the same direction. The membranellar band, 

 especially at the level of the basal bodies, showed the sharpest 

 effect and therefore seemed to be a site of vigorous oxidation. 

 Methylene blue gave essentially the same results and Child felt 

 confirmed in his demonstration of a metabolic gradient in Stentor, 



Confirmation also seemed to be evident in the work of Monod 

 (1933) who studied the differential susceptibility of different parts 

 of the cell in Stentor and other common ciliates to ultraviolet 

 radiation. Again there was an antero-posterior gradient in disinte- 

 gration of the ectoplasm. 



Although Weisz ( 1 948d) confirmed Child in regard to the gradient 

 response of stentors to KCN and KMn04, he stood strongly 

 against Child's interpretation. This was largely because he had 

 found (Weisz, 1948a, c) that, other factors being the same, the rate 

 of oral regeneration and subsequent growth of fragments was 

 independent of the level of the body from which they were taken, 

 though of course the shape of Stentor does not admit of much 

 variation in this regard. 



Holding that primordium formation and rate of growth are more 

 indicative of metaboUc state than is cellular disintegration, Weisz 

 denied the whole concept of metabolic gradients as applying to 

 Stentor and also questioned its applicability to other forms. He 

 gave a new twist to these experiments by studying the disintegra- 

 tion of fragments of stentors in KCN. Anterior pieces disintegrated 

 from the anterior end the same as whole animals. Posterior frag- 

 ments began disintegrating not at their anterior ends but at the 

 holdfast. And middle pieces started disintegrating first in the 

 region of the contractile vacuole. Hence he viewed the Stentor cell 

 as a heirarchy of structures which vary in their susceptibility to 

 external agents, and this is a function not of any cellular gradient 

 but of the organization of those structures, although it is stretching 

 the point to say that the contractile vacuole is more highly organized 

 than the lateral ectoplasm of middle fragments. 



In answering Weisz, Child (1949) seems to be saying that 

 Stentor is not a good form for studying this problem an^^vay 

 because it does not have the long and cylindrical shape of worms 

 and hydroids. But we shall shortly describe that there are a great 

 variety of simple salts and other substances, not directly related to 



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