80 MaynAarn M. MErTcALF, 
“The time from opening the animal to the killing of the Opalinas 
varied from a few minutes to about four hours. This made little, 
if any, difference with tbe nuclei. Those examined fresh showed 
apparently the same condition. It is possible that the nucleus rests 
in this mitotie condition, or possibly the death of the host may have 
induced mitosis. We have been unable to determine this point for 
lack of material. Our older living salamanders do not seem to contain 
many living Opalinas, and the young animals, which are usually so 
abundant here in the west, have been unobtainable during the last 
two years.” 
“The killing fluid used was one that we can recommend highly 
for protozoan nuclei, namely a mixture of equal parts of KLEINEN- 
BERG’S picro-sulphuric acid (strong formula) and concentrated sublimate 
in five per cent acetic acid. The stains were CoNKLIN’s picro- 
haematoxylin, used very weak and prolonged several days, or else 
different carmine stains followed by combinations of Lyons blue and 
pieric acid in absolute alcohol. The clearing was done with different 
grades and combinations of Bergamot oil and Xylol, followed by gum 
damar introduced in the lump.” 
“We have not found these Opalinas in any other of the several 
species of Amphibia which we have examined here.” 
Only three points in this letter call for comment. The presence 
of the Opalinas in the large intestine, as well as in the rectum, 
was probably due to the hosts having died some hours previous to 
the removal of the Opalinas. In living frogs, if in good health, the 
parasitic Opalinas are restrieted to the rectum. Often after the 
death of the host some of the parasites pass into the intestine. In one 
instance, in a frog with badly inflamed stomach and intestine, I have 
found Opalinas in the intestine while the frog was still alive. Pro- 
bably in the living Adlystoma the Opalinas are confined to the rectum. 
The suggestion that mitosis in these Opalinas may have been 
induced by the death of the host is a natural one, but is very 
improbable, for in other species of Opalina, though abnormal con- 
ditions, such as cultivation outside the host, tends to bring on mitosis, 
this change in the nuclei appears only after one or more days and 
never in many individuals, whereas the Opalinas here described all 
show nuclei in mitosis. It seems clear that the nuclei rest in a 
mid-mitotie condition. 
The fact that these Opalinas are more abundant in young sala- 
manders taken in the fall than in adults — presumably examined in 
