100 
BULLETIN OF THE UNITED STATES FISH COMMISSION 
Th«y are of very imiforin size and shape. In their usual position they appear to be 
flattened or disc shaped ; when turned on one edge they are seen to be lenticular. 
The outline is always elliptical, the longer diameter being about 0.0139 millimeter, 
the shorter, 0.0110 millimeter. Their thickness was not so certainly made out, but in 
one individual, which appeared to be standing on one edge, it was about 0.008 milli 
meter. Fig. 5 is a sketch of an ideal section along the shorter diameter. 
Near one end of each there are two transparent, pyriform, refractile bodies, their 
smaller ends converging and directed toward the nearest border. These are the 
twinned vescicles of Balbiani and the polar capsules of Biitschli. In many cases 
smaller supplemental refractile bodies were seen at the base of the pyriform bodies. 
This phenomenon is shown in Fig. 2. These have the position but not the appear- 
ance of Biitschli’s dark grannies. The remainder of the interior is filled with a clear 
viscid fluid, which in some cases has a few small refractile particles in it. The walls 
are rather thick and quite firm, with a sharp, clear, entire outline. In optical section 
there is often the appearance of a third refractile body behind the pyriform vescicles. 
This is due, in the fresh specimens, to the thick transparent walls and the viscid 
refractile fluid interior. When treated with certain reagents this viscid fluid seems to 
separate from the wall so as to appear as a nuclear body. This appearance is shown 
in Fig. 7, which represents one of the psorosperms after having been treated with 
acetic acid. The two filiform ai)j)eudages, said to be characteristic of these animals, 
were not seen satisfactorily in fresh specimens. Some specimens were placed in one- 
half per cent, osmic acid for a few minutes and afterward examined with a high luagui 
fyiug power, but no appendages were distinguishable. It is likely that a longer con- 
tinuance in osmic acid would be followed by better results, as the material in the walls 
is but slowly attacked by even concentrated sulphuric acid. 
Other examples after being fixed to a slide by means of alcohol were stained with 
methyl green, and subsequently with eosiu. The pyriform vescicles were not stained 
deeply, while the walls were deeply stained and differentiated from the plastic, homo- 
geneous material which fills the interior. 
In some of the individuals that had been subjected to the action of osmic acid 
and were \flewed under especially favorable conditions a small pore was discerned at 
the apex of each of the pyriform vescicles. These are evidently the orifices from which 
the filiform appendages issue. The osmic acid preparations also enabled me to per- 
ceive for the first time a feature that was afterwards seen in specimens treated with 
sulphuric acid and which appears to be constant, viz, a low rounded ridge which ex- 
tends along the edge of the animal from tip to tip. Fig. 6. This feature is noticed and 
figured by Biitschli in his account of myxosporidse from the gills of certain fresh water 
cyprinoids. 
Specimens were kept in sea water for about ten days and observed from time to 
time, but no noteworthy changes were observed to take place. Although the connec- 
tive tissue of the mass underwent maceration, the psorosperms showed but little indi- 
cation of the effect of maceration. At the end of the eighth day a few were noticed 
ill which the walls seemed to have given way, in which case the pyriform bodies were 
liberated. The latter were still intact. 
Upon treating a small piece of the abnormal tissue with sulphuric acid brisk effer- 
vescence ensued. As the psorosperms remained with but little change under this 
severe treatment, the effervescence was plainly from some other source. Another piece 
