SCHIZAMCEBA SALMONIS 
7 
ment the chromatin collects in several large masses on the nuclear membrane, 
which eventually become rounded and, following disintegration of the nuclear 
wall, form the karyosomes of the newly-formed cyst nuclei. The karyosomes 
are connected at one side with the nonchromatic nuclear wall by a mushroom-shaped 
achromatic structure, in which are embedded numerous chromatic granules. The 
cyst nuclei divide several times by promitosis, during which the karyosome is 
divided into two equal parts without losing its identity. Eventually the cysts 
divide into several multinucleate cells, which separate and form new cysts like the 
original. The trophozoites are found only in the stomach; the cyst in both stomach 
and intestine of salmonid fishes. 
DISTRIBUTION 
That this species is widely distributed is shown by the fact that, although 
it has been under observation for only a short time and but little attention has 
been paid to this feature, it has already been found in several species of trout, 
including the rainbow ( Salmo shasta), the brook trout (Salvelinus fontinalis) , and 
the brown trout (Salmo far io) , at the White Sulphur Springs (W. Va.) and Wythe- 
ville (Va.) hatcheries. The cysts of this ameba have also been found in the young 
of the chinook salmon ( Oncorhynehus tschawytscha ) and the silver salmon ( Oncorhyn - 
chus Jcisutch) from several hatcheries on the Pacific coast. Dr. Emmeline Moore 
also reports that it occurs in trout at a number of the New York State hatcheries, 
where the cysts have been confused with those of Octomitus salmonis. It is very 
evident that this ameba is widely distributed among the Salmonidae. 
RELATION TO HOST 
There is, as yet, no evidence that Endamcnba salmonis is directly harmful 
to the host, although it is sometimes present in very large numbers. In fact, it 
has been observed in several instances that the parasites were exceptionally abundant 
in fish that appeared to be in excellent condition, while there were only a few amebae 
in sick fish from the same lot. This difference in the abundance of the parasites 
was probably due to the fact that the sick fish were taking little if any food, since it 
has been found that the ambse rarely occur in numbers in the stomachs of fish that 
have been without food for several days. But while apparently not directly in- 
jurious, at least under ordinary conditions, they are doubtless of considerable im- 
portance in nutrition, since when abundant they must consume appreciable quan- 
tities of food that would otherwise be utilized by the host. 
OTHER AMEByE IN TROUT 
In addition to Endamceba salmonis, another ameba has been found in the 
stomach and intestines of trout in several instances. As in the case of S. salmonis, 
the vegetative stages were found in the stomach while only cysts were observed in 
the intestine. In appearance this species is quite distinct from S. salmonis, especi- 
ally as regards the structure of the nucleus, which always contains a prominent 
karyosome even in the ameboid stage (figs. 38 and 39). The protoplasm is more 
