GROWTH AND DIVISION 83 



the connection between the two components was quite intimate; 

 and the complex then divided as a unit, often separating into two 

 proters and a doublet opisthe. 



When the larger partner had already entered division and 

 carried an early division primordium, its division was still delayed 

 and the anlage was resorbed after grafting. Again, this response 

 could be attributed to the operation, because control animals also 

 resorbed the primordium with cutting injuries and did not re- 

 commence division until 6 hours later. In the graft combination, 

 primordia then appeared in both large and small components 

 which divided simultaneously about 6 to 7 hours later. 



If the dividing partner was in mid-stage division with a well 

 formed membranellar band, grafting then resulted only in arrest 

 of the anlage and not in its resorption. An induced primordium 

 then appeared in the small component which divided along with 

 the larger. But if the divider had already advanced to the stage at 

 which mouthparts were beginning to form at the posterior end of 

 the primordium, then no secondary anlage was induced and fission 

 was largely confined to the side of the original divider. Yet there 

 still could be some effect on the smaller component. If the macro- 

 nuclear nodes of the divider had not yet clumped, then those of the 

 small partner coalesced also. Weisz further stated that a division 

 furrow sometimes extended around the smaller component, but I 

 suspect from what has already been said concerning blockage of 

 the division line that in these cases the furrow passed above or 

 below the smaller graft. 



These results were interpreted by Weisz as demonstrating that 

 pre-divisional animals or stentors in early stages of fission can 

 induce fission in graft partners which otherwise would not have 

 divided, and that this induction is produced by some influence 

 emanating from the dividing cell and passing to its partner. I am 

 obliged to say, however, that these demonstrations are in need of 

 further clarification and control before such conclusions can be 

 asserted with certainty. If dividers. are grafted to regenerators 

 one might expect that division would be the more easily induced 

 because the non-dividing partner already carries a primordium; 

 instead, I found that fission occurred only on the side of the 

 divider and did not include the partner, which merely regenerated. 

 Furthermore, combinations like Weisz's did not always yield the 



