7 -ON CERTAIN WART-LIKE EXCRESCENCES, OCCURRING ON THE SHORT 
MINNOW, CYPRINODON VARIEGATUS, DUE TO PSOROSPERMS. 
BY EDWIN LINTON. 
[Plate XXXV.] 
On August 20, 18S9, while at the U. S. Fish Commission laboratory, Wood’s Holl, 
Mass., I obtained a specimen of the short minnow [Cyprinodon having 
upon its body several fungoid, wart-lihe excrescences, which, upon examination, proved 
to be occasioned by the presence of psorosperms. These parasitic protozoans are 
regarded as related to the Gregarinidie on account of their resemblance to the psendo- 
navicellae of that family, but their exact nature is not yet well understood. They have 
been recorded by naturalists from a number of European fishes, among which are sev- 
eral sjiecies of perch {Oyprinus rutihis, G. erytliropthahnvs, and C. lettciscus), other 
perch-like fishes {Lticioperca)^ the white-fish [Goregonus fera), and some of the fresh- 
water minnows {Gyprinodon). They have also, doubtless, been observed hitherto on 
kindred American fishes, but so far I have been unable to find any literature describ- 
ing their occurrence in America. 
The specimen of Oiyprmndmi 'Turief/utus, which I had the opportunity of examining 
at Wood’s Holl,-had three of these fungoid masses on the left side of the body and 
one on the right. The latter is shown in the sketch. Pig. 1. 
One of those on the left is also shown iu part in the same sketch, where it projects 
above the line of the back. This mass was about 6 millimeters iu diameter ; it was sit- 
uated a short distance behind the eye and above the operculum ; another behind the gill- 
slit and extending diagonally backward and downward was 10 millimeters long and 4 
millimeters broad ; another behind the latter and near it was 4 millimeters long and 2^ 
millimeters broad. These masses are irregular in outline and elevation ; they protrude 
as much as 3 millimeters above the general surface of the body ; they do not appear to 
consist of closed cysts. 
The abnormal growth is apparently confined to the superficial muscular and sub- 
cutaneous tissue. Sections carried througli one of the masses reveal clusters of pso- 
rosperms lying in the interstices of the connective tissue, and patches of dark pigment, 
with a few capillary vessels. The skin of the host overlying these tumors is more or 
less cracked and broken, and the scales scattering. 
When a piece of one of these almormal growths was placed on a slide in water 
and gentle pressure applied myriads of oval bodies, such as are shown in Figs. 2-4, 
were set free. These spore-like bodies when liberated lay motionless at the bottom 
of the water. During all my observations on them no movements were discovered. 
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