Parasites of Frogs and Toads. 
429 
then takes place, and one mass travels to each of the daughter 
blepharoplasts. In this region the chromatin masses subsequently 
fragment into small granules, a new nuclear membrane is formed, 
and the two daughter nuclei thus acquire the structure of the 
original nucleus. During this period, the blepharoplasts have 
been gradually drawing further and further apart — -but still re- 
main attached by the connecting rod. The external shape has 
also been greatly modified, being now roughly sausage-shaped — 
a nucleus and blepharoplast lying at either end, and the rod 
running longitudinally from one blepharoplast to the other. The 
new flagella are formed by out-growths from the blepharoplasts — 
two from either blepharoplast. The dividing organism remains 
for a short time in this condition, and then suddenly is constricted 
in two at the middle. Two rounded daughter monads result, each 
with an axial rod formed from a half of the rod which lay between 
the two blepharoplasts and was formed in the division of the 
parent blepharoplast. 
It will thus be seen that the axial rod is reformed at each 
division, and does not arise in the daughter monads by splitting 
of the pre-existing organ. It is a product of the division of the 
blepharoplast. 
If the organisms are taken from the gut of their host, or leave 
it in the faeces, they invariably die. Inside the host, however, 
they are able — under conditions which have not been ascertained — 
to form cysts. These cysts no doubt serve for the dissemination 
of the parasites. 
The cysts are very small, and vary in size somewhat. Before 
encystment, the nucleus undergoes a change of structure, whereby 
a large karyosome is formed in it. The animal later becomes 
motionless, and loses its flagella. A cyst membrane is produced 
and gradually hardens. Inside the cyst, the axial rod degenerates. 
At a later stage, the nucleus becomes drawn out in a longitudinal 
direction so that it extends almost from one end of the cyst to the 
other. The blepharoplast persists as a little diplosomic body 
lying upon the nucleus. 
In spite of much careful observation, I have never been able 
to observe an autogamy in the cysts. It will, indeed, be seen 
from my description that they differ entirely from those described 
in allied forms. 
(2) Trichomonas hatrachorum Perty. 
I have reinvestigated the structure of this parasite, and find 
that it corresponds closely with that of the Trichomastix just 
described. The chief difference is the presence of an undulating 
membrane in place of the posterior flagellum. It arises from the 
blepharoplast and possesses a basal rod-like support which stains 
