EXCRESCENCES ON THE SHORT MINNOW. 
101 
of the tissue was subjected to the action of strong pola sic hydrate. This dissolved 
out the connective tissue and left a residue which consisted of the psorosperms, still 
imaflected by the reagent, and small calcareous iiarticles of extremely irregular shape. 
Some of the latter are shown in Fig. 14, and three of the calcareous particles more 
highly magnified, along with some of the psorosperms, in Fig. 15. The walls of the 
l)Sorosperms withstand the action of concentrated sulphuric acid and of a saturated 
solution of potassic hydrate for a long time. When treated with iodine they stain 
yellowish brown. When placed in glycerine tbe walls of the psorosperms collapse. 
The action of sulphuric acid was most successful in bringing out certain details of 
structure which had otherwise escaped detection. One of the first effects of concen 
trated suliihuric acid which was observed, and which resulted almost immediately after 
application of the acid, was to cause the protrusion of two filamentary a])peudages 
from the anterior end, i. e., the end at which the polar- vescicles lie. In some cases 
these threads are nearly straight, in others they are undulate, and a few were thrown 
into a more or less close spiral. 
The latter gives some hint of the retracted condition of these threads, and confirms 
Balbiani’s view that the twinned vescicles which are found in all the psorospermse 
serve normally as sheaths for the threads which, according to that author, alwaj^s 
issue from the end of the animal near which the converging ends of the vescicles lie. 
Zschokke (9) figures a psorosperm from Goregonus fera, which bears a very close 
resemblance to these from the short minnow. The two filiform appendages, however, 
appear to be exceptional, in that they issue from the end opposite the polar vescicles. 
The i3Sorosperms described by Zschokke occur in cysts from the size of a pea to that of 
a walnut, fixed firmly among the muscles. 
These cysts are white, oval, inclosed in a thick envelope without apparent struct- 
ure and containing a whitish licpiid of milky appearance. Examined under the 
microscope thousands of psorospermre maybe seen disposed among the granular proto- 
plasm. The psorospermse described by Biitschli from the fresh-water cyprinoids were 
also inclosed in a cyst, in which were calcareous particles. 
In some cases the psorosperms which have been treated with concentrated sul- 
phuric acid have ejected the polar vescicles bodily with the filaments extruded (Figs, 
12, 13). The threads are of the same diameter throughout and are not extremely slen- 
der. The distal ends are truncate. The organs, therefore, do not resemble flagella. 
The appearance of one of these vescicles with its thread is strikingly suggestive of 
the nematocyst of a ccelenterate. The threads staiu yellowish-brown with iodine. 
One psorosperm was observed which api^eared to have three threads, two normal 
and a third at the opposite end. This aiipearance was at first thought to be due to 
one of the free vescicles getting behind the body of a i^sorosperm. Such a posterior 
thread has been noticed by other observers and is figured by Biitschli (8). 
When treated with acetic acid a nuclear vescicle was clearly defined in the appar- 
ently homogeneous tissue behind the polar vescicles. A similar appearance was noticed 
in a few that had lain in sea water for a period of eight days, None of the reagents 
employed brought out the diagonal strise represented by Biitschli in his figures of the 
polar vescicles of the myxospores from the fresh-water cyprinoids, and which are due 
to the thread coiled up in a spiral within the vescicle. In other respects Biitschli’s 
figures of cyprinoid myxospores bear a very close resemblance to these psorosperms 
from Cyprinodon variegatus. 
