Opalina. BPH | 
those of Rana temporaria. In the chapter on infection experiments, 
page 314, I have shown that cross infections are very easily secured. 
In view of this fact it seems hardly safe to accept ENGrLMAnn’s 
report of O. ranarum from Rana esculenta as surely establishing that 
that species naturally occurs in this host.]| ENe@rnMann’s work 
definitely settled the fact that the nuclei of the multinucleated 
Opalinae are true nuclei. He regards Anoplophrya and Hoplitophrya 
as transitional forms between Opalina and other IJnfusoria. He 
sought unsuccessfully to find the manner of origin of the cysts 
in the rectum of the frog. 
ZELLER, the following year (1877) published a very accurate 
paper describing for five species (O- ranarum, O. obtrigona, O. dimi- 
diata, O. intestinalis and O. caudata, n. s.) 1) the rapid transverse 
and oblique [really longitudinal] divisions in the spring, within the 
frog’s rectum, by which the Opalinas become minute; 2) the cysts 
in the rectum of the frog and the process of encystment; 3) the cysts 
in the rectum of the tadpole; 4) the character of the animals hatched 
from the cysts; 5) their growth to adult character. Good descriptions 
of the form and structure of the adults are given. ZELLER is the 
first to describe the nucleoli and their behaviour in mitosis and 
gives also the first good description of the disc-shaped refractive 
spherules. In studying the multinucleated species of Opalina he 
found the cysts in the rectum of the frog 
to be multinucleated (usually 4 nuclei); in 
the recta of the tadpoles he found both multi- 
nucleated and uninucleated cysts, the latter 
with large nuclei, as ENGrLMaANN described. 
He figures a minute “abnormal” individual Text Fig. XV. 
of O. ranarum from the rectum of the tad- 2®"0#®’s figure of a minute 
: . O. ranarum from a tadpole 
pole [which was probably a microgamete or o¢ pana a 1b 
a microgamete mother-cell (Text Fig. XV),  waspossibly a microgamete 
but he did not so interpret it, nor did he or a microgamete mother- 
observe copulation]. He figured and briefly ell, though the tail bears 
described a large form occurring with 0. cu 
dimidiata in Rana esculenta, which he said might be either a new 
species or a form of O. dimidiata. {NERESHEIMER has since named 
this form O. zelleri.| This, the finest of all the papers upon Opalina 
will long serve as the starting point with all students of the genus. 
CerTES (1880) discusses the presence of glycogen in the Jnfusoria, 
either in the form of refractive spherules or in solution in the endo- 
