Opalina mitotica. 93 
Explanation of the figures. 
All figures are of Opalina mitotica. Figures 1—6, 8, 10 and 11 
are magnified 270 diameters: figures 7, 9, 12—15 are magnified 1114 
diameters. 
Ellenner 2% 
Figs. 1—5. Full sized binucleate individuals of the usual sort. 
Fig. 6. An individual just formed by longitudinal division. The 
irregular contour on one side of the posterior half of the body is the 
usual distortion caused by longitudinal division, the two individuals of the 
pair pulling apart usually with considerable difficulty. 
Fig. 7. A more enlarged drawing of the nucleus of the individual 
shown in Fig. 6. The nucleus is in the typical “resting condition” for 
this species i, e. is dumbbell-shaped and in the anaphase of mitosis. Ten 
chromosomes appear in one end, the other end bears eleven chromatin 
bodies, but two are connected and probably represent one chromosome. 
Fig. 8. An individual recently formed by longitudinal division. 
Fig. 9. A more enlarged drawing of the nucleus of the individual 
shown in Fig. 8. The nucleus has begun to divide preparatory to pro- 
ducing a typical binucleate individual. Each half of the dumbbell-shaped 
nucleus is in the irregular equatorial plate stage of mitosis characteristic 
of the binucleate Opalinas. By the time the two halves of the dumbbell- 
shaped nucleus have completely separated, loosing their connecting thread, 
each portion will itself have assumed a dumbbell form and will be resting 
in the typical anaphase, as seen in Fig. 7. Ten chromosomes were seen 
in one end of the nucleus. Only eight could be made out in the other 
end, the left portion of this end of the nucleus not being clear. 
Fig. 10. A small individual which has just been formed probably 
by transverse division. It contains the anterior of the parent nuclei. This 
