1911.] 



Infusorian Micronucleus in Regeneration. 



335 



and oc. 2. The merozoa were isolated in nutritive solution on hollow-ground 

 slides in a moist chamber. Fresh or one-day-old hay infusion was used as 

 culture fluid, with or usually without the addition of a few Golpidia. 

 Stylonychia thrives quite well on a diet of bacteria and the nuclear relations 

 are not obscured in preparations by the presence of the nuclei of ingested 

 prey. 



Nuclear phenomena were examined in glycerine mounts of animals fixed 

 and stained by Schneider's acetocarmine, which gives a perfectly clear picture 

 of the nuclei. 



In all the experiments I am about to describe, the hind end of the animal 

 was removed by a transverse cut. Only in a few cases did the cut pass 

 between the two members of the meganucleus ; the most interesting results 

 were obtained when the nuclear apparatus was left untouched. 



These were the earlier experiments ; the removal of the anterior end was 

 attempted later, when it was found that the stock culture was in a very 

 heterogeneous condition as regards the nuclear relations of its individuals, and 

 the results of these cuttings will not be dealt with. As far as could be 

 ascertained, they are in full agreement with those which follow. 



The result I shall establish is briefly this : — In the regeneration which 

 follows merotomy, multiplication of micronuclei may occur, and this increase 

 may cause the regenerated individual to have more micronuclei than the number 

 typical of the species or race. 



Stylonychia mytilus (O.F.M.) is a hypotrichous ciliate of considerable 

 differentiation of parts (see fig. B). 



The nuclear apparatus consists of a bimembered meganucleus, to the left 

 of each node of which lies a micronucleus. There is a variety with four 

 micronuclei, but with this I have had nothing to do. There is a fine 

 connection between the members of the meganucleus, but it is usually invisible 

 in stained and cleared preparations. 



I shall use the following formula to express the nuclear relations : — 

 M, am : M, bm. 



M stands for a member of the meganucleus, and m'for a micronucleus, a 

 being the number lying by the anterior M, and b the number by the 

 posterior M. 



As is implied thus, the anterior M is written first. The normal condition 

 of the animals with which I worked was 



M, lm : M, Ira. 



Or written more simply, 



M, m : M, m. 



