CHAPTER V 



GROWTH AND DIVISION 



I. Growth 



Division in Stentor is of course usually preceded by growth to 

 the definitive size. Authentic structural growth and de-growth 

 occur, as well as stretching of parts. The first is seen, for example, 

 as increase in the number of lateral clear stripes with their fibrous 

 elaborations ; the second, in resorption of striping or macronuclear 

 nodes under various conditions ; and the potentialities for stretching 

 are shown when small patches of ectoplasm come to cover the 

 surface (see Fig. 25A) or when isolated nodes change from round 

 to spindle form (see Fig. 82A). We still have no comprehensive 

 understanding of growth in the individual stentor cell and no 

 investigator has yet addressed himself directly to this problem, 

 but the pigmented stentors, especially, offer many advantages for 

 such a study. In the first place, most stentors contract into a 

 sphere and a fair estimate of their volume can be obtained by 

 measuring one diameter. Grafted pairs can be identified by their 

 pigmented stripes, which are often seen to increase both in number 

 and in length (Fig. 11 a). Natural markers sometimes are found in 

 the cortex of the cell and indicate growth by their apparent dis- 

 placement (b,c). Similar markers for following the growth of the 

 ectoplasm could be made by small disturbances of the pigment 

 striping, for the smaller these disarrangements are the longer they 

 persist before correction (Schwartz, 1935). 



Differential growth of major cell constituents is to be seen in 

 the recovery of endoplasm in stentor "skins" (see Fig. 25B), as 

 well as in the rapid recovery of the macronuclear mass when all 

 but a single node has been removed from the cell (see Fig. 86c). 

 In normal stentor cultures I have occasionally found specimens 

 which were much longer than usual, with half the normal number 

 of lateral stripes, as if growth in length had occurred at the expense 

 of growth in width. On isolation this disparity was later corrected. 



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