Grafting of Tuhularia 349 



Experiment I. Removal of the region of the distal tentacles 

 before the ridges appear. The hydranth and about 5 mm. of the 

 stem below it were removed from twenty-seven pieces of stems 

 whose length averaged 3.5 cm. These pieces were left undis- 

 turbed for eighteen hours. At the end of this time the circulation 

 in the oral end was rapid but no ridges had been laid down. A 

 piece .7 mm. long was then removed from the oral end of each 

 piece (Fig. 22, A), thus separating the region in which the distal 

 tentacles would appear later, {A) from the longer proximal piece 

 {B) on which the proximal row would have developed. The 

 pieces were isolated and their later behavior observed. The 

 iFollowing table gives the results from twenty-five pieces, two of the 

 twenty-seven having been lost. 



SERIES I A 



Complete hydranth 5 



Distal tentacles only lo 



No regeneration lo 



Total number 25 



By complete hydranth I mean distal and proximal tentacles, and 

 reproductive organs. No stalk developed on these small pieces. 



In the second series, twenty-two pieces were cut, the length of 

 the distal piece {A) was increased from .7 mm. to i mm., thus 

 including part of the region between the two rows of tentacles. 

 The time between the first and second operations was the same as 

 that in Series i. 



SERIES 2 A 



Complete hydranth 9 



Distal tentacles 9 



No regeneration 4 



Total number 22 



Comparing Series I and 2, it will be seen that with an increase 

 in the length of the distal piece {A) there is an increase in the pro- 

 portion of complete hydranths. 



