REGENERATION IN URONYCHIA 105 



normal but after 72 hours A had one abnormal cirrus; this how- 

 ever was only temporary, the cell being entirely normal the fol- 

 lowing day. B divided on the third day but one of the products 

 was only quarter size and both died the following day. 



In experiment 37 the cell was cut longitudinally as shown in 

 fig. 9, and from 6 to 8 hours after division. After 24 hours A 

 was large, normal and active; B was also normal and active but 

 small and died after 48 hours. 



In cells midway between division periods therefore, the power 

 of regeneration is much better developed than in cells immediately 

 after division. 



4. Cells cut during the process of division 



A. In the early stages and before the compact dividing nucleus 

 is Jormed. 



If the cut is transverse or oblique and not directly through the cen- 

 ter, the larger fragment with the micronucleus divides in the original 

 plane. All three fragments regenerate into normal organisms one 

 of which has no micronucleus. 



Experiments 9, 11, 12 and 13, were cells cut transversely after 

 the first external traces of division were seen. At this period 

 the nucleus is still distributed, (cf. fig. 2) but new cirri are form- 

 ing in the anterior half and at the bases of the old cirri in the pos- 

 terior half. Experiment 12 is typical. Here the cell was cut 

 above the mid line as shown in fig. 10. After 3 hours A had not 

 begun to regenerate, while B was dividing in the original central 

 line of the cell. After 18 hours however, A was completely regen- 

 erated although somewhat abnormal in shape. B had divided 

 forming one large and normal cell B' and a much smaller quarter 

 size cell, B" . After 42 hours A was somewhat smaller but per- 

 fect and very active, B' was large and perfect; B" as before. 

 After 66 hours A was still smaller and emaciated B' had divided 

 while B" remained as before. Finally, after 90 hours, A and B" 

 died. Experiment 14 gave exactly similar results. In experi- 

 ments 9 and 11, the cuts were almost directly through the plane 

 of future cleavage. In no. 9 only two cells were formed; in 



