REGENERATION IN URONYCHIA 109 



original plane in every case. Of this set, no. 69 is typical and 

 well illustrates the reaction to the operation at this period of 

 division. The cell was cut as shown in fig. 14, above the line of 

 division. After 6 hours A was complete and B had divided, B' 

 being very small and with only six cirri, while B" was complete 

 and normal. After 24 hours A was completely regenerated; 

 B' one-eighth size and transparent but normal in structure; 

 B" was perfect. All were killed. A, B' and B" had perfect 

 macro-nuclei, but A had no micronucleus. 



In experiment 70, alone, regeneration failed. The cell was cut 

 just above the plare of division. After 6 hours A divided in the 

 original plane, and B was perfect. After 24 hours neither A' nor 

 A" were regenerating and all were killed. The macronucleus 

 in B was degenerating, A ' had a perfect macronucleus and micro- 

 nucleus and would have regenerated if not killed. A" had no 

 nucleus at all and only half of an adoral zone, but had large cirri. 



In experiment 59 the cell was cut obhquely and in such a way 

 that only a small fragment of the macronucleus was included. 

 After 4 hours A had not regenerated while B had divided. After 

 24 hours A was perfect, so also was B' , but B" was only one- 

 eighth size and not fully regenerated. 



C. If cut during the later phases of division. In experiments 

 10, 35, 60 and 62 the cells were cut after division of the micro- 

 nucleus and during division of the macronucleus. The cleavage 

 furrows were conspicuous, indicating a condition of approximately 

 half to three-qu-arters of an hour before final separation. 



In nos. 10 and 35, the plane of the cut was close to the plane of 

 division. In both cases only two cells were formed and one cell 

 in each case became abnormal after 24 hours. In these cases the 

 macronucleus was degenerated and distributed throughout the cell. 



In experiment 62 the cell was cut longitudinally through the 

 center as shown in fig. 15. After one-half hour the fragments 

 were nearly divided ; after one hour both were divided. After 24 

 hours all four fragments were very lively but none had regenerated. 

 After 48 hours A' was dead while the rest were still unregenerated. 

 All were then killed and no nucleus was found in any fragment 

 although there was much chromatin in granule form distributed 



