1911.] Infusorian Micronucleus in Regeneration. 



337 



The posterior micronucleus m* was in an early stage of division. (Fig. 1.) 



(2) Merozoon killed 3f hours after section. 



M, m : M, mm. 

 The posterior micronucleus was in division (mm). (Fig. 2.) 



(3) Merozoon killed 3 hours after section. 



M, mmf : M, mf. 



The micronuclei marked mf were in process of reconstruction after 

 division. v Fig. 3.) 



(4) Merozoon killed 2>\ hours after section. 



M, mmf : M, mf. 

 Eeconstruction of mf had gone a little further than in (3). (Fig. 4.) 



(5) Merozoon killed 18£ hours after section.. 



M, 2m : M, m. (Fig. 5.) 



Most probably this is a case where the posterior micronucleus had 

 divided. Fig. 4 shows that in that case two micronuclei would be found 

 anteriorly. 



There is a possibility that this is merely one of the abnormalities which 

 became frequent later, and that the animal was so constituted before the 

 operation. 



(6) Merozoon had divided 27 hours after section. Both daughters were 

 killed. Micronuclear division had presumably taken place during 

 regeneration, and the six micronuclei found altogether in the two animals 

 were formed by the division of the three present after regeneration was 

 complete. I do not attempt to explain in detail the irregular distribution 

 to the daughters, or the unusual positions of some of the micronuclei in 

 the cell. 



It is not known which of the individuals arose from the anterior part of 

 the merozoon. (Figs. 6 and 7.) 



2M, 4m, and 2M, 2m. 



(7) Had divided 46 hours after section. 



Each daughter had divided 24 hours later, and a sample of each was 

 killed. (Figs. 8 and 9.) 



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

 By the next day each had divided again, and samples were again killed, the 

 nuclear relations in both cases being : — 



M, m : M, 2m. 

 An accident caused the loss of both survivors. 



