Opalina. 329 
Gruser (1885a) in a discussion of multinucleate protozoa, refers 
briefly to Opalina, saying that the fragmentation of the multinucleate 
Opalinas in the spring, by which a generally uninucleate condition 
is reached before encystment, is not comparable to ordinary binary 
fission. [The encepted forms usually have two to four nuclei.] 
GruBeEr (18850) in a discussion of artificial division in infusoria, 
refers briefly to Nusspaum’s (1884) work, mentioning the fact that 
Opalina fragments into dissimilar pieces which later by regeneration 
reach normal form. 
Birscuit (1886) describes and figures the alveolar structure of 
the endoplasma of O. ranarum and says that the ectoplasma shows 
similar structure. 
PriTzNeR (1886) gives a [too schematic] account of the division of 
the nuclei in O. ranarum. He interprets the refractive spherules as 
algae. He showed clearly that the nuclei of 0. ranarum divide mi- 
totically. The true nucleolus was not seen. The absence of centro- 
somes and the persistence of the nuclear membrane were observed. 
Splitting of the chromosomes was [mistakenly] said to occur during 
a typical equatorial plate stage. 
Nusspaum (1886) gives a brief outline of the life history of 
O. ranarum after EnartmMann and Zeuupr. He says the least 
particle of foecal matter causes a culture of Opalina quickly to die. 
(Others, myself included, have found that cellures with foecal matter 
live longer than those without.} He describes form, mode of 
swimming, and structure. He says that division apparently stops 
during the winter sleep of the host: that animals ready for encyst- 
ment have four or more nuclei. [I find frequently one, two, or three, 
as well ar four or more]: division is described at considerable length; 
the products of division are not always alike; sometimes there is 
division into three pieces; at the temperature of the room division 
occupies forty to forty-five minutes; division of the body is in- 
dependent of the division of the nuclei, but division of the nucleus 
does not occur during division of the body. [I have not found the 
last statement correct for my preparations]; the direction of the 
mitotic spindle with reference to the planes of the body is very 
various; the nuclei show no interrelation in their divisions, dividing 
at different times without reference to one another: he found multi- 
nucleated and uninucleated cepts in the recta of tadpoles and 
thought it probable that the latter are derived from the former by 
fusion of nuclei: the nuclei of the young Opalinae in the tadpoles 
divide mitotically: he confirms Zevuer that some Opalinae in the 
