REGENERATION IN URONYCHIA 111 



In experiment 27 the nearly divided cell was cut through the 

 connecting strand as in no. 26. In 27A the second cut was longi- 

 tudinal. After 18 hours A' remained a mere fragment while A" 

 had six cirri and an abnormal peristome. After 42 hours A' 

 had not regenerated at all and A" was imperfect in shape although 

 complete. No. 27B was also cut longitudinally, B' being very 

 minute was lost. After 18 hours B" had seven cirri and part 

 of the adoral zone. After 42 hours it had not regenerated further 

 and was killed. 



In experiment 50 two halves of a dividing cell were separated 

 artificially as before. A was cut longitudinally, while the sister 

 cell was lost. In 24 hours A' had regenerated into a one-quarter 

 sized individual while A" failed entirely to regenerate. In 72 

 hours A' had reached full size and was normal in all ways. 



In experiment 65 the posterior part was cut obliquely through 

 the macronucleus. After 24 hours B' was one-fourth, B" was 

 one-eighth size and both were normal. 



E. Cells cut two or 7nore times during division. In experiment 

 6 the cell was in the mid phase of division and cut twice, the cen- 

 tral fragment being lost. The anterior fragment died within 24 

 hours, but the posterior fragment regenerated perfectly. 



In experiment 17 the cell was in the early phase of division when 

 cut twice. The anterior fragment was little more than the adoral 

 zone and was lost ; the central portion regenerated within 24 hours 

 but the posterior fragment failed entirely to regenerate. After 72 

 hours the central portion divided. On killing and staining the 

 posterior portion no nucleus was found. 



Experiment 19 was more satisfactory and decisive. Here the 

 dividing cell was first cut transversely through the adoral region 

 of the anterior cell, and second, transversely just posterior to the 

 original division plane. After one hour A had regenerated two 

 big cirri, B' had normal but crowded cirri, and C had a new and 

 complete adoral zone. After 18 hours A had abnormal cirri, B 

 had no adoral zone, while C was normal and active. After 42 

 hours A had regenerated into a perfect cell of one-quarter size, 

 B remained without regeneration but was lively, and C was nor- 

 mal. After 66 hours A was dead, B remained the same and after 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 10, NO. 2 



