BACTERIOLOGY OF THE OYSTER. 6 



chamber, at the anal orifice. This latter opening was ^ to % of an 

 inch above the lower end of the partition which separated the two 

 chambers. A loopful of B. prodigiosus was then placed in the gill 

 chamber, and loopfuls were removed from the cloacal chamber and 

 plated at intervals of ten minutes for one hour, and then at the end of 

 two hours and three hours. B. prodigiosus is a non-motile organism 

 and was chosen because of its ease of identification and because in all 

 our work extending over four years we have never isolated it from 

 oysters. 



No red colonies were found in the two control samples from the 

 two chambers, but every plate made from the cloacal chamber after 

 the introduction of the B. prodigiosus into the gill chamber showed 

 colonies of B. prodigiosus. 



Exp. 2. The above experiment was repeated with another 

 oyster and B. prodigiosus was again found in the cloacal chamber ten 

 minutes after its introduction into the gill chamber. 



Series II. 



Exp. 1. In another set of experiments four oysters were used. 

 In these oysters five holes were bored as indicated in the plate 

 shown on opposite page. Three of these holes opened into the gill 

 chamber (1, 4, 5). Another hole (2) was made into the cloacal 

 chamber near the anal orifice, and the last hole (3) opened on the edge 

 of the mantle about an inch above the anal orifice. 



All four of these oysters were inoculated in hole No. 5 with a loopful 

 of B. prodigiosus. Loopfuls from the other holes were inoculated 

 upon agar slants at two minute intervals, for ten minutes and then 

 every five minutes, for twenty minutes, making a total of 30 minutes 

 in each case. The result is seen in the following talile : 



