336 



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



The irregularities which cropped up in the stock culture were the 

 occurrence of animals of the types : — 



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



Cases of Eqxial Section. — In these I include all cases in which the plane of 

 section passed between the two members of the meganucleus. Each of 

 the merozoites thus obtained is capable of regeneration and subsequent 

 division. 



ad. memb. 



Fig. B. — Stylonychia mytilus (semi-diagrammatic). Ventral view, x 300. 

 ad. memb., adoral membranellae. M, mega-, m, micro-nucleus. 



ft:, frontal cirri. c.v., contractile vacuole. 



an., anal cirri. marg., marginal cirri. 



The initial condition is M, m, but regeneration includes segmentation of 

 the M into two members, and the division of m. The normal relation, 

 M, m : M, to is thus attained. 



The division of the micronucleus might, from a consideration of this case 

 alone, be regarded as part of the mechanism of organic regulation, since its 

 effect is to restore the normal proportions. 



Gases of Removal of a Plasmatic Portion from the Posterior End. — In none 

 of these was the nuclear apparatus disturbed by the section. 



(1) Merozoon killed 4£ hours after section. 



M, to : M, m*. 



