264 BULLETIN OF THE BUREAU OF FISHERIES. 



lack of facilities this has not been determined with certainty. They can often be seen 

 to move in a straight line for a considerable distance, the movement being accompanied 

 by a sinuous bending of the rod which may temporarily assume an S-shape. One of the 

 characteristic movements is to turn one end slowly in a circle, the other end remaining 

 stationary and forming a pivot on which the entire rod revolves. This movement is 

 very noticeable along the edge of scales or bits of infected tissue when placed on a slide. 

 Large numbers of bacteria can usually be seen in such places with one end attached 

 while the free end moves back and forth in the manner described above. 



Another characteristic is the formation of small chains of bacteria from one object 

 to another while on the slide. The chains are formed by the bacteria arranging them- 

 selves in rows joined end to end, the ends slightly overlapping. Usuallv these chains 

 consist of two or three rows of bacteria arranged parallel to each other, but occasionally 

 there may be but a single row. Bacteria can be seen continually moving back and 

 forth along these living chains in a very characteristic manner. 



However, the most characteristic movement and the one which usually serves to 

 make the species easily recognizable is well shown when a little material scraped from a 

 lesion is placed on a slide in a drop of water. Possibly owing to the pressure of the 

 cover glass the bacteria soon collect in immense numbers on the edge of bits of infected 

 tissue, scales, etc. Here they form short columnlike masses, each column being sepa- 

 rated a short distance from its neighbor (figs. 248 and 249). The columns usually taper 

 slightly toward the free end, which is ordinarily rounded but in rare cases may be pointed. 

 In some cases the ends of the columns may be distinctly enlarged. In favorable cases 

 a whole series of these columns may form along the edge of a scale. These columnar 

 masses of bacteria are very characteristic, and it is apparently in this way that they free 

 themselves from the gelatinous matrix in which they are embedded while growing on 

 the fish. Along the sides and rounded ends of the columns can be seen bacteria with 

 one end attached while the free end waves back and forth in the manner already de- 

 scribed. Bacteria continually break loose from the columns while others swarm out 

 to take their place. Occasionally short chains may be formed extending out from the 

 ends of the columns, the bacteria at the ends continually becoming free but often man- 

 aging to work their way back along the chain after a time. When free, the bacteria at 

 first exhibit a peculiar vibratory movement somewhat different from the Brownian 

 movement and which, when once seen, is easily recognized. After being free a short 

 time they usually collect on the underside of the cover glass and become perfectly 

 motionless. 



These characteristic swarming movements of the bacteria are no doubt continually 

 taking place on the fish, at least in late stages of the disease, for it has been found that 

 badly diseased fish are continually shedding bacteria in enormous numbers. 



Owing to the fact that a variety of stains was not available the staining reactions 

 of the bacteria were not studied in detail. They stain readily with fuchsin and Giemsa's 

 stain, the stained preparations appearing perfectly homogeneous. 



No evidence of sporulation has been observed, and that they do not form spores 

 is also indicated by the fact that the bacteria are easily killed by chemicals and drying. 



All attempts to grow the bacteria on artificial media have so far proved unsuc- 

 cessful. During the summer of 1918 the writer made several attempts to isolate the 

 bacteria, and these experiments were continued by Miss Mackenzie during the summer 



