No. 6.] PROPORTIONATE STRUCTURES IN STENTOR. 727 



\J I 



cut surface in a most irregular way, yet this does not appear to 

 interfere with the subsequent regeneration ; and after a time 

 the stripes appear to be more regularly arranged. That a 

 certain amount of absorption takes place, and possibly also 

 development of new stripes, seems probable, but I have not 

 studied these changes in any detail. It would be interesting 

 to find out if in cross-pieces of the body the number of the 

 stripes remains the same and their size becomes smaller, or 

 whether the number of the stripes is proportionately reduced. 



On several occasions I have tried to graft together pieces of 

 different stentors, but the exposed surfaces close so quickly 

 that I have not been able to get the pieces to unite. It does 

 not seem altogether improbable that the result could be 

 brought about by cutting two stentors at the same time, one 

 about the other. A lucky cut might bring two exposed inner 

 surfaces together, and they might stick to each other, but 

 so far I have not been able to carry out successfully this 

 experiment. 



In a few cases the stentor was split partially in two pieces, 

 but generally the halves soon fuse together. It is of some 

 interest to find that, although the peristome was cut in two 

 and had reunited, a new peristome was not produced, showing 

 that the operation alone does not initiate the changes that lead 

 to the development of a new peristome. 



The development of a new peristome in a piece that contains 

 a part of the old one appears to be due to the lack of propor- 

 tion between the old part (even when it contains all the essen- 

 tial parts of the peristome) and the rest of the piece. This 

 result is unique, since in all other forms in which a part of an 

 old organ remains the new organ regenerates from that part. 

 In stentor this does not occur, but a new organ is produced. 

 It is important to observe, however, that this is the character- 

 istic way in which stentor produces a peristome, so that the 

 organisms make use of a process that already exists. The 

 reduction in size of the old peristome in pieces from the 

 anterior end is the result that has most interested me. It 

 seems to be due to the withdrawal of material from the ante- 

 rior region to form the body and stalk of the new stentor. 



