No. 6.J PROPORTIONATE STRUCTURES IN STEXTOR. 325 



innate tendency to complete the typical form. We are not 

 justified, I believe, in drawing the conclusion, as Gruber has 

 done, that preformed elements of the peristome exist in the 

 nucleus and must be set free in order to initiate the develop- 

 ment of a new peristome. 



Lillie has found that the smallest piece of Stcntor polymor- 

 plins that becomes a perfect form is equal to a sphere of about 

 80 /A in diameter. The average size of the stentors was equal 

 to 230 /J-. This makes the volume of the smallest stentor 

 about Jy of the normal. For Stcntor cocrnlcns the smallest 

 stentors measured 90 /u, (== T 1 T mm.), the average normal 

 stentor 280 //, (=^ mm.). Therefore the former is about 

 J T of the latter. 



Although I have not worked specially on this problem, yet 

 I have obtained some small stentors that were proportionately 

 smaller than those obtained by Lillie. Thus one individual 

 measured when extended .25 x .08 mm., and when contracted 

 into an oval or nearly into a sphere .08 x .08 ( = = j\ mm.). 

 The larger normal stentors measured about .4 x .32 x .32 when 

 contracted. Although it is only possible to give a general 

 estimate of the relative size of these two individuals, the smaller 

 cannot be over J- 4 - of the former. It would be a mistake to 

 infer from this, as well as from Lillie's calculations, that the 

 latter came from a piece ^ or even ^V of tne original stentor. 

 The protoplasm of stentor is so vacuolated that a piece losing 

 the fluid in the protoplasm might become much smaller than 

 when first removed. 



Lillie states that he believes that it would be possible to 

 obtain a smaller individual of 5. cocrnlcns than T T T mm. The 

 one that I obtained was in fact somewhat smaller, vis., -^. 2 mm. 

 The difference in our results depends, therefore, rather on the 

 size of the normal average stentor with which the comparison 

 is made than on the smallest individual obtained. Lillie says 

 that he does not think there can be much difference in the 

 absolute size of the smallest stentors, whether one uses the 

 largest or the smallest normal specimens. It seems to me that 

 this may or may not be true, according to what factors may 

 enter into the result. 



