Opalina. 363 
In reality all were stained equally dark. Coros. subl.-acetic acid, iron haematoxylin. 
< 808 diameters. 
Fig. 86. A longitudinal section of a nucleus in a telophase of mitosis. Four 
of the chromosomes are seen to have at their edges rows of more or less elongated 
granules. These granules are not arranged in pairs. Most of the longitudinal 
fibres of chromatin are seen to be very granular. The finer chromatin threads 
and most of the achromatic structures are omitted. In this nucleus it was im- 
possible to sharply distinguish between chromatin granules and achromatic granules. 
Coros. subl.-acetic acid, iron haematoxylin. >< 1600 diameters. 
Fig. 87. An abnormal individual showing a great lateral swelling in which 
the endosare was evenly granular, and the ectosare apparently structureless. There 
were no endosare spherules in the swollen area. They were abundant in the 
rest of the body, but are not drawn. The finer structures of the nuclei were not 
clear enough to draw. Coros. subl.-acetic acid, DeLarrenp’s haematoxylin. 404 
diameters. 
Fig. 88. A very stocky individual. In the nuclei only the chromosomes 
and chief chromatin fibres of the upper surface are shown. Coros. subl.-acetic 
acid, DELAFIELD’s haematoxylin. > 556 diameters. 
Fig. 89. A very stocky and abnormal individual, with four nuclei each in 
a telophase of mitosis. Two of these, seen in end view, do not show their mitotic 
condition. In the right hand nucleus the chromatin is abnormally compact. In 
the nucleus in the middle most of the granules drawn are probably achromatic. 
In the other two nuclei only the chromosomes and the chief fibres of the chromatic 
spindle are drawn. Coros. subl.-acetic acid, Dr LArrenp’s haematoxylin. 556 
diameters. 
Fig. 90. An individual with almost completely degenerated nuclei. Coros.- 
subl.-acetic acid, DeLartenp’s haematoxylin. > 400 diameters. 
Fig. 91. A probably abnormal individual with nuclei in a condition charac- 
teristic of the multi-nucleated Opalinae, but never, I think, found in normal in- 
dividuals of O. caudata. Coros. subl.-acetic acid, D&ELArFIELD’s haematoxylin. 
<< 808 diameters. 
Fig. 92. An individual with abnormal nucleus. Coros. subl.-acetic acid, 
borax carmine. < 404 diameters. 
Plate XXI. 
Abnormalities, Opalina intestinalis and O. obtrigona. 
All figures are reduced one-fifth, to the magnification indicated. 
Figs. 93—98. Opalina intestinalis. 
Fig. 93. Outlines of the nuclei and the anterior end of a young individual. 
< 404 diameters. 
Fig. 94. The same nuclei as those shown in Fig. 93. The aggregation of 
the chromatin into large irregular masses is abnormal], although the animal was 
killed immediately after removal from the host. Coros. subl.-acetic acid, DeLaFrieLp’s 
haematoxylin. >< 1600 diameters. 
Fig. 95. The anterior end of an individual where posterior nucleus is ab- 
normal, as is shown by the aggregation of the chromatin into a few dense compact 
masses. This was first observed upon staining with acetic-carmine, after which 
the animal was stained with DeLarrep’s haematoxylin and drawn. In the anterior 
