282 M. M. Mercatr 
the cyst, the free action of the cilia apparently being of great 
assistance in all divisions at all times of year, helping to separate 
the daughter cells. I have, however, found, two cysts of O. caudata 
each containing two individuals either entirely distinct or so nearly 
so that the connection between them could not be observed (Fig. 
256, Pl. XX VI). Ze_LeR and LOEwEntTHAL describe cysts of O. ranarum 
containing individuals in division, and Dornermy quotes PrzEsSMECKI 
as having seen the animals in the cysts divide into several offspring. 
I have seen nothing of this multiple division in the cysts. 
The cysts do not need to lie in water in order to produce suc- 
cessful infection. 
Tadpoles eat, often eagerly, the foeces of frogs and toads, so 
that it is easy to infect them. Ofter feeding cysts to the tadpoles, 
the cysts will be found throughout the whole alimentary canal in- 
cluding the rectum. The little Opalinae leave the cysts usually in 
the rectum of the tadpole but occasionally they are found in the 
small intestine. Wherever hatched the little Opalinae collect at 
the upper end of the rectum of the tadpole, just as the larger forms 
do in the rectum of the frog or toad. They mostly keep together, 
lying between the foecal mass and the rectal wall, a few individuals 
only being found scattered through the foecal mass. 
Ihave studied the spring reproduction in O. zntestinalis, O. caudata 
and O. dimidiata, and will describe the phenomena for all three species, 
beginning with O. intestinalis. 
The minute forms of O. itestnalis ready for encystment do not 
have the body form characteristic of larger individuals, but look 
more like Amoeba limax (Figs. 121—129, Pl. XXIL). They are ciliated, 
but the cilia are unusually delicate, being distroyed by acetic car- 
mine, while the cilia of larger individuals in the same preparations 
are only considerably injured. The narrow posterior end of the 
body often shows a peculiar minutely lobulated appearance similar 
to what one often sees at the posterior end of an actively moving 
Amoeba proteus (Figs. 122, 123, Pl. XXII). Ectosare and endosare 
are distinct and each contains the usual spherules. The last division 
before encystment is almost always longitudinal (Figs. 121, 122, 
Pl. XXII) but possibly may sometimes be transverse (Fig. 123, 
Pl. XXII). I have not had the good fortune to see the whole 
process of encystment in any species. ZELLER describes the process 
for O. ranarum as follows (p. 359). — “Die Tierchen schwimmen zwar 
noch eine Zeitlang mit groper Lebhaftigheit wmher, dann aber werden 
sie zusehends langsamer in ihren Bewegungen, ziehen sich kugelformig 
