10 BACTERIOLOGY OF THE OYSTER. 



carried to the mouth (hole No. 4) while others escaped the mucus 

 and passed through the gills into the cloacal chamber (hole No. 2). 

 A further study of table No. 1 will show that the bacteria passed with 

 the currents for this particular bacterium was non-motile and so 

 could not have reached the different points by its own activity. 

 Moreover, the interval of time which separated the inoculation of the 

 branchial chamber and the subsequent recovery of the bacterium 

 from the different holes in series II was only 4 minutes in all, except 

 two cases when it was six and fifteen minutes. The distance between 

 holes 5 and 4, 5 and 2, and 5 and 3, in all cases was at least an inch, 

 in most cases, more. In series III the bacterium was recovered from 

 all the holes in four minutes in one case and ten minutes in the other . 

 The rate of travel of bacteria varies with the species, temperature, 

 etc., but it is inconceivable that a bacterium of the speediest variety 

 could move a distance of over an inch in four minutes by its own activ- 

 ity. In the case in hand, i. e. a non-motile bacterium, it is out of 

 the question. 



It is also seen in table No. 1 that in two cases B. prodigiosus was 

 isolated from hole No. 2 before it was recovered from hole No. 1. In 

 the two other cases they were recovered at the same time. While this 

 is not conclusive it leads the writer to beiieve that the bacteria 

 isolated at hole No. 1 had previously passed through the gills and the 

 cloacal chamber and back into the branchial chamber by the return 

 current. The results of the experiments in series III lend support to 

 this view. The bacteria did not go directly from hole 5 to hole 1 

 because the currents along the edge of the gills is too strong to allow 

 a bacterium to pass in that direction. An examination of this current 

 under the microscope will convince anyone that a bacterium could not 

 travel in that direction. 



A study of table No. 2, which shows the appearance of B. prodigiosus 

 in the gill chamber after the inoculation of the cloacal chamber, 

 shows that the organisms appeared at hole No. 1 and later at hole Nos. 

 5 and 4. This is the order of time in which a current from the cloacal 

 chamber and taking the direction of the arrows of the edges of the 

 gills would appear at holes Nos. 1, 5 and 4, in the branchial chamber. 



From the foregoing facts it is plain that the gills are not bacteria 

 proof; that bacteria can and do pass from the gill chamber to the 

 cloacal chamber through the gills and moreover, that bacteria may 

 pass from the cloacal chamber to the gill chamber without passing 

 through the gills. It is seen that we have a complete circle of currents 



