922 REPORT OF TIIE COMMISSIONER OF FISH AND FISHERIES. 
urinary bladder of Lucius lucius, consisting of small free masses lining 
the internal surface of the organ, the second consisting of drawn-out, 
chain-like masses in the midst of the tissues of the organ. The second 
he believes to be merely a more advanced stage of the first. When the 
parasite is only slightly developed its presence is recognizable only by 
small opaque streaks in the otherwise transparent bladder, on opening 
which the myxosporidium is found upon its internal surface. In other 
cases small white prominences are found, presenting a transition between 
the large mammillated masses described by Balbiani, and which can 
attain 10mm.in thickness. Sections showthe myxosporidium intimately 
united to the epithelium. The latter soon becomes broken up and the 
plasmic chains insinuate themselves between the fibers of the connec- 
tive tissue. 
By serial sections one can follow progressively the march of the para- 
site into the tissues. These last allow of separation and stretching of 
the fascie, such change being progressive and slow. Soon, however, 
under the continuous pressure produced by the growth of the invading 
mass, the fibers arrive at the limit of extensibility and finally rupture. 
Thus are formed irregular spaces, in the middle of which one finds the 
débris of the tissue of the organ, surrounded by the myxosporidia. 
During this time spores are formed. They finally almost entirely 
replace the protoplasm. In other parts of the same mass earlier and 
intermediate stages can be seen. In the air bladder, as in the kidney, 
the distinction between the ectoplasm and endoplasm is little evident 
and, beyond the fact of the absence of nuclei from the ectoplasm, it is 
difficult to find characters to separate these layers. 
(b) Of the external surface, Balbiani' gives, as the results of his 
investigations, the following account of the development: 
Of all freshwater fishes the tench is most frequently affected with Myzxosporidia 
and at all seasons. This, together with the transparency of the fins of the young, 
renders it especially favorable for investigation. Balbiani frequently observed 
upon the fins, mingled with developed psorosperms, small amcsboid bodies of very 
variable size. These move like the most agile amebe (e. g., A. diffluens), 9 changes 
of form occurring in less than 15 minutes; temperature had great influence, heat 
accelerating, cold retarding. The pseudopodia were large and obtuse, the mass 
appearing lobed, as in 4. diffluens. Unless obscured by fat globules (numerous in 
the later stages), the nucleus is plainly visible, particularly at the time of the exit 
of the mass from the spore. It is the nucleus of which Biitschli has proven the 
existence in the interior of the psorosperm (cf. p, 208). There is no contractile 
vacuole, and from this point of view these bodies differ from the ordinary amebee. 
While thus wandering over the fins, the small ameboid bodies absorb nutriment, 
grow, show more or fewer fatty globules, tend to take a rounded oval, or sometimes 
irregular form with expansions and lobes, and to surround themselves with a thin 
envelope easily visiblein water. As the water penetrates the fin tissue, the ameeboid 
movements become more and more slow and finally cease. Independently of its 
thin proper membrane, the small mass is encysted in the same manner as other 
foreign bodies, by the connective tissue of the host. 
1 Journ, de Microgr., 1883, vu, pp. 2724. 
