Opalina. 359 
as is shown by its position (compare Figs. 40—42). Coros. subl.-acetic acid, borax 
carmine. X< 460 diameters. 
Fig. 44. An individual in transverse division. The nuclei are in an anaphase 
of mitosis. Coros. subl.-acetic acid, Denarietp’s haematoxylin. > 460 diameters. 
Plate XVIIL 
Opalina intestinalis. 
All figures are reduced one-fifth, to the magnification indicated. 
Fig. 45. An individual with two nuclei each in a prophase of mitosis. 
Coros. subl.-acetie acid, Drnarrevp’s haematoxylin. Drawn at 1010 diameters, 
reduced to 08 diameters. 
Figs. 46—48. Three optical sections, through the upper, middle and lower 
thirds respectirely, of the posterior nucleus shown in Fig. 45. In Fig. 46 most 
of the fibrils shown belong to the chromatin network. In Fig. 47 the varicose 
fibrils in the center of the figure are optical sections of the films of the achromatic 
foam. In Fig. 48 only the chromatin masses and a few of the chromatin fibres 
are shown. X 1600 diameters. 
Fig. 49. An individual with two nuclei in an early stage of mitosis. Espe- 
cially in the posterior nucleus, one sees that the chromosomes are arranging them- 
selyes in two adequatorial rows preparatory to migration to the poles of the 
nucleus. The distinct and rather coarse fibers are fibers of the chromatin spindle. 
Most of the achromatic structures and the finer chromatin threads are omitted. 
Coros. subl.-acetic acid, DetarieLp’s haematoxylin. >< 808 diameters. 
Figs. 50—52. Three optical sections, through the upper, middle and lower 
thirds respectirely of the posterior nucleus shown in Fig. 49. The coarse varicose 
longitudinal chromatin fibres of the spindle are well seen in Fig. 50. Fig. 51 
shows the emarginate form of the ends of the chromatin spindle (compare Fig. 49). 
Fig. 52 shows that not all of the chromosomes have yet been formed from the 
chromatin ribbon (spireme). The achromatic structures lying in the deeper layer 
of the upper third of the nucleus are omitted from Fig. 50. In Figs. 50 and 51 
one sees that the chief longitudinal fibres of the chromatin spindle are attached 
to each pole of the nuclear membrane. The nucleolus lies in the lower part of 
Fig. 52. It is darkly shaded, not because it was heavily stained, but to make it 
seem to lie near the top of the section. >< 1600 diameters. 
Fig. 53. An individual with its nuclei each in an anaphase of mitosis. 
Eight chromosomes were present in each end of each nucleus. Most of the achro- 
matic structures and the finer chromatin fibres are omitted in each nucleus. Coros. 
subl.-acetic acid, DELAFIELD’s haematoxylin. >< 808 diameters. 
Fig. 54. A daughter cell with its single nucleus in a late anaphase of 
mitosis. Some of the chromosomes are constricted transversely into two unequal 
portions (compare Fig. 53). All structures are omitted except the chromosomes 
and the thickest chromatin fibres. Coros. subl.-acetic acid, DeLarieny’s haema- 
toxylin. >< 808 diameters. , 
Fig. 55. A nucleus, in an anaphase of mitosis, in which the fibres of the 
chromatin spindle were more delicate, more numerous and less distinctly longi- 
tudinal than usual. Except in the center of the nucleus, the achromatic structures 
are omitted. Here some of the chromatin fibres are omitted, leaving a “‘window” 
through which the vacuolated nucleolus and the films of the achromatic foam are 
seen. The nucleolus is seen to lie in an enlarged alveolus of the achromatic foam, 
