326 MORGAN. [VOL. II. 



The conclusion that a piece ^ or even J T of the entire 

 animal can produce a new individual can give only a most gen- 

 eral idea of the relative size of the smallest piece, since more 

 depends on the size of the normal individual than on that of 

 the smallest pieces, and there is for stentor a very wide range 

 of size that may be called normal. A large normal individual 

 may contain eight times the volume of a small normal indi- 

 vidual. More significant, therefore, is the absolute size of the 

 smallest piece capable of regeneration, and in this respect my 

 results are practically in accord with those of Lillie. 



Several experiments were made in which pieces were cut in 

 two longitudinally. In a longer or shorter time most of the 

 halves produced a new peristomial band that became a new 

 peristome. As this experiment did not give promise of much 

 that is new, it was tried in only a few cases. 



A few casual observations made during the course of the 

 work may be briefly mentioned. The stentors were observed 

 dividing on several occasions, but Johnson's excellent figures 

 and account of these stages leave nothing new for me to add. 

 I have often noticed that after division the two products are 

 found attached side by side, and if they are not disturbed a 

 little colony may arise in the same spot. Several times I have 

 observed that two individuals that have been formed by division 

 of one of the regenerated posterior pieces were unequal in size, 

 although I do not know whether the smaller individual was 

 the distal or the proximal one. 



As Gruber has pointed out, the first steps in the process of 

 division and of regeneration are the same, and this holds also 

 for the physiological replacement of the old peristome. In all 

 cases a peristomial ciliated band appears on tlic side and moves 

 forward around the anterior end to become the new peristome. 

 We have here another illustration that shows that during the 

 process of regeneration the factors that appear in the normal 

 growth may take part in the regeneration, and this relation 

 appears to hold for unicellular as well as for multicellular 

 forms. 



In many cases, especially where a somewhat oblique cut has 

 been made, the superficial blue stripes come together over the 



