366 M. M. Mercaur 
Fig. 135. An optical section of another cyst from the same preparation. 
Most, perhaps all, of the ectosare spherules have been extruded and lie between 
the body and the wall of the cyst. Acetic-carmine. 990 diameters. 
Fig. 136. An optical section of another cyst from the same preparation, 
showing in the nucleus one large and one small chromatin sphere and a central 
mass of granules. Between the cell body and the cyst wall is a mass of debris 
probably derived from degenerated ectosare spherules. Acetic-carmine. < 673 
diameters. 
Figs. 137—139. Opalina caudata. Sections (2 «) of cysts from the rectum 
of an adult Bombinator pachypus. All of the nuclear structures present are 
accurately drawn. In Figs. 137 and 138 all of the chromatin seems to be gathered 
into the chromatin spheres. In Fig. 159, in addition to the chromatin sphere, ten 
small chromatin masses are seen. Others were present in the adjacent sections. 
Coros. subl.-acetic acid, DrELarretp’s haematoxylin. > 1334 diameters. 
Figs. 140—143. Animals hatching from the cysts in the rectum of a tadpole 
of Bombinator pachypus five hours or less after ingestion of the cysts. Ectosare 
spherules are shown (shaded) in Fig. 140. In the same figure granular debris is 
seen in the cyst. The boundary between ectosarc and endosare is indicated by 
dotted lines. Most of the cilia were distroyed by the acetic acid and the currents 
caused in making the preparation; all which were seen are drawn. The details 
of nuclear structure were not well shown. Acetic-carmine. >< 673 diameters. 
Figs. 144 and 145. Macrogametes or macrogamete parent-cells') from the 
rectum of a tadpole of Bombinator pachypus, infected 6 days. Few cilia were 
drawn in the original sketch for Fig. 144, the rest having been filled in later. 
The endosare spherules are shown in Fig. 145. No nucleus was visible in this 
darkly stained animal. Possibly it had degenerated. Acetic-carmine. 673 diameters. 
Fig. 146. A living dividing individual from a tadpole of Bufo vulgaris, in- 
fected 60 hours. Endosare spherules (shaded) and ectosare spherules (unshaded) 
are shown. The nuclei were not clear. A second, more anterior, seemed to be 
present at a lower level, but I could not be sure of it. The long and sparce 
cilia make it probable that (after not less than two divisions) this individual 
would have given rise to microgametes. >< 673 diameters. 
Fig. 147. A free-hand sketch of a very active, dividing macrogamete mother- 
cell (it may be a parent-cell) from a tadpole of Bufo vulgaris, infected 36 hours. 
The two daughter cells are of the same size. They were slightly flattened, one 
being seen more in edge view. Extruded excretory granules were seen dragging 
behind one daughter cell. 
Figs. 148 and 149. Optical sections of macrogametes or macrogamete parent- 
cells from a tadpole of Bombinator pachypus, infected 136 hours. But few cilia 
were in the original sketch for Fig. 148, the rest having been supplied later. 
Each nucleus shows four chromosomes. <Acetic-carmine. >< 673 diameters. 
Fig. 150. An optical section of a macrogamete from a tadpole of Bombinator 
pachypus, infected 43 hours. Acetic-carmine. > 673 diameters. 
') I use the word parent-cell to indicate a cell which after one or more divisions 
will produce gametes. The word mother-cell is used for a cell whose next division 
will give rise to gametes. I realize that the phraseology is not satisfactory, but 
with the understanding that parent is entended to include grand parent or still 
earlier generations, it may do for the purposes of the present paper. 
