374 M. M. Mercaur 
Figs. 305 and 306. Macrogametes from a tadpole of Rana esculenta, infected 
97"/, hours. In the second figure endosare spherules are shown, and also a chro- 
matin sphere extruded from the nucleus into the cytoplasm. Acetic-carmine. 
x 673 diameters. 
Figs. 307 - 309. Divisions in the formation of the microgametes; from a tad- 
pole of Rana esculenta, infected 80'/, hours. The number of chromosomes seemed 
in some nuclei five, in others six. Probably six is the correct reduced number of 
chromosomes for O. dimidiata. Some of the nuclei were not sufficiently clear to 
draw and are left empty. In Fig. 309 the division may be abnormal, but in this 
species the nuclei are so independent of one another that the lack of synchronism 
in their division in this case may not indicate abnormal condition. The endosarc 
spherules are shown in all figures. From life. > 673 diameters. 
Fig. 310. A living microgamete, with unusually long tail, from a tadpole 
of Rana esculenta, infected 8 days. There was no swelling at the tip of the tail 
such as is usually seen in microgametes in this and other species. >< 673 diameters. 
Fig. 3511. An individual which seems to be a microgamete mother- cell, 
from a tadpole of Bufo vulgaris, naturally infected for at least three weeks. The 
tail is some what contracted by acetic carmine. Copulation was found among the 
Opalinas in this tadpole, this being by far the oldest infection in which copulation 
or microgametes were seen. Acetic-carmine. X< 673 diameters. 
Fig. 312. A living copulating pair from a tadpole of Rana esculenta, infected 
98 hours. XX 673 diameters. 
Fig. 313. A pair of living individuals from a tadpole of Rana esculenta, 
infected 80'/, hours, showing a dividing microgamete mother-cell attached to 
another cell of about the same size. The manner of the attachment and the 
condition of the nuclei indicate that this was either a chance connection or an 
abnormal attempted copulation. There was no change after three-quarters of an 
hour. Free-hand drawing. 
Figs. 314—318. Zygotes from tadpoles of unnoted species (probably Rana 
esculenta, otherevise the fact would have been noted), infected 7 days, except the 
host for the animal shown in Fig. 117,. which was infected 97'/, hours. The nuclei 
were not sufficiently well stained to allow accurate drawing of the chromosomes 
or chromatin masses, which were so numerous as to obscure one another. The 
posterior nuclei shown in Figs. 315 and 316 are the synecaria. Possibly all the 
nuclei shown in Fig. 318 have come from the syncarion, the posterior daughter 
having completed a second division with which the anterior nucleus is still engaged ; 
or the macrogamete may have contained originally three nuclei. The smaller size 
of the posterior nuclei makes the first interpretation much the more probable. 
The details of nuclear structure are not adequately shown. The chromatin masses 
were so numerous as to obscure one another. Acetic-carmine. >< 673 diameters. 
Fig. 319. An individual from the same preparation as Fig. 318. The anterior 
nucleus from its shape would seem not to be a syncarion. It may be abnormal. 
The chromatin is not accurately drawn. Acetic-carmine. > 673 diameters. 
Fig. 320. Another individual from the same preparation, in which the anterior 
nucleus is the syncarion with the spindle form which persists until after at least 
one division. The chromatin could not be accurately drawn. Acetic-carmine. 
X< 673 diameters. 
Figs. 321—324. Young individuals from tadpoles of Bufo vulgaris, naturally 
infected for an unknown period. Still larger individuals, with twice as many 
