340 



Mr. K. R Lewin. The Behaviour of the [Sept. 15, 



It is quite possible that every division produced daughters respectively : — 



M, 2m : M, m, and M, m : M, 2m. 



The experiments so far described make a series which proves definitely 

 that the regenerative processes involve in some cases a division of the 

 micronucleus. 



When a Stylonychia is cut equally the mitosis always here associated 

 with regeneration restores the normal number of mieronuclei. In these 

 experiments, too, there is a reorganisation of the meganucleus, which does 

 not occur when a purely plasmatic portion of the animal is removed. 



In the numbered series of experiments, on the other hand, the mitosis 

 is no regulative action, but results in the regenerate having an abnormally 

 large number of mieronuclei. 



More than 50 per cent, of the experiments in plasmatic removal gave 

 negative results with regard to nuclear division, i.e., the fully regenerated 

 merozoa had the normal nuclear relation, M, m : M, m. 



Two cases must now be given in which there is indicated a division of 

 the anterior micronucleus, i.e., that farther from the plane of section. It 

 is possible that this occurred more often, but in view of the heterogeneity 

 of my material daring the later experiments I cannot be certain of this. 



(8) Merozoon killed 2|- hours after section. 



M, m* : M, m. 

 m* is in an early stage of division. (Fig. 10.) 



(9) 1 hour after section the frontal cirri could not be seen. The animal 

 was in continual rotation. Between 3 and 5 hours after section the adoral 

 membranellse were withdrawn. 7 hours after section the adoral membranellae 

 were regenerated. No anal cirri seen. 22^ hours after section the ciliation 

 was normal, but the posterior end of the regenerate was rather pointed. 

 Staining revealed the fact that the anterior micronucleus had divided : — 



M, m : M, 2m. 



The infusorian was rather more transparent than is usual, and careful 

 observation before cutting had made me fairly confident that the original 

 relations were normal : — 



M, m : M, m. 



That the posterior micronucleus did not divide is in no way surprising, for 

 as is mentioned above, in more than 50 per cent, of the experiments there 

 was no mitosis caused. 



