REGENERATION IN URONYCHIA 



101 



1. Uronychia cells cut immediately after division 



If the cell is cut immediately after division and before the nucleus 

 begins to fragment into the normal condition, there is but little power 

 of regeneration and then only when both nuclei are present. In 

 some cases there is no regeneration at all. 



Experiment 28. Both cells were cut at once after division; the 

 anterior cell was cut longitudinally and in such a plane that no 

 nuclear material was included in one of the fragments. This 

 failed to regenerate, but the other fragment formed a perfect cell 



4 A 



4 B 



Fig. 4A Experiment 42. The cell, immediately after division, was cut ob- 

 liquely as shown. Neither fragment regenerated although the sister cell divided 

 twice in the next three days. 45. Experiment 28. The cell was cut immediately 

 after division. B regenerated perfectly, A failed to regenerate although the nucleus 

 underwent the first stages of reorganization {A, on right). 



within 24 hours, normal in size and form. The posterior cell was 

 cut transversely as shown in the diagram (fig. 45). The macro - 

 nucleus was almost equally divided between the two fragments, 

 the micronucleus was retained in the posterior fragment. The 

 latter regenerated perfectly within 24 hours, the anterior frag- 

 ment failed to regenerate although it continued to live for 48 

 hours when it was killed for the determination of the nuclear 

 structure. 



Experiment 36. Here the plane of the cut was longitudinal. 

 Macronuclear material was retained in each fragment, while the 



