Opalina. 3a 
and they were equally abundant in the two regions. Light causes 
no injury to Opalina. A frog was opened in faint light and the 
Opalinas in the rectum were placed in two cultures, one remaining 
in the dark, the other being placed in bright daylight. No sub- 
sequent difference between the two cultures was observed. He found 
that Opalinas in a culture swim indifferently toward the warmer 
or toward the cooler area. 
In a second paper (1890) VreRworn showed that 0. ranarwm, 
stimulated by an electric current, swims toward the anode. 
Parker (1891 and subsequent editions). describes briefly the 
structure and life history [so far as then known] of 0. ranarium. 
(The only error is the statement (after ENGELMANN) that] the little 
Opalinae, which hatch from the infection cysts in the alimentary 
canal of the tadpole are uninucleated. 
PerRRIER (1893) refers to the difference between ectosarc and 
endosare in O. ranarum, to the presence of paraplasmatic bodies [re- 
fractive spherules] in the cytoplasm, to the process of encystment, 
to the fact that nuclei and cytoplasm divide independently, to the 
process of mitosis which is described according to Prrrzner’s abser- 
vations [and therefore inaccurately]. 
VeRworRN (1896) mentions again the anodic galvanotropism of 
O. ranarum and says further that under stimulation from a strong 
current the side of the body toward the kathode becomes clearer 
and more strongly refractive; that the granules of protoplasm and 
the nuclei withdraw more and more from that edge of the body; 
that smal] hyaline vesicles soon appear there; that the cilia of that 
side are then destroyed; and that the contour of that part of the body 
then becomes uneven. There follows immediately a granular disin- 
tegration of the side of the body toward the kathode. VERworN 
believes that the anodic galvanotropism of O. ranarum is due to a 
contractile irritation of the kathodic side of the body [later shown by 
Date (1901) and WaLLenGcRrEn (1903) to be a mistaken interpretation]. 
Detace & Herovarp (1896) [mistakenly] interpret ZELLER’s 
figure of the form [which NeresHEemeER has named] 0. zelleri, as in- 
dicating the presence of remnants of an excretory organ. 
Lors & BupGetr (1897) quote VeRworn’s description of the 
fragmentation of the kathodic side of the body of O. ranarum under 
strong electric stimulation, ascribing this to the action of acid; they 
believe that this anodic reaction of Opalina is due to the fact that 
it is always studied in physiological sodium chloride solution. {[PirrEr, 
1900, has shown the error of this assumption. | 
