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which, on Drigalski medium incubated at 37 C., are capable of 

 yielding blue colonies like B. typhosus. I have examined a 

 considerable number of Burnham oysters, of Colchester oysters, 

 of clean Dutch oysters, of Whitstable oysters, and others ; and 

 I have not found in them any bacteria which, incubated on 

 Drigalski medium at 37 C. for 24-72 hours, form such blue 

 colonies. On three occasions when examining clean oysters, I 

 have been, however, greatly puzzled by the appearance in the 

 Drigalski plates of blue colonies with violet margin, which, by 

 their size, by their slightly irregular contour, and their more or 

 less conical form, and uniformly granular appearance, looked 

 very like those of B. typhosus. And the difficulty became: 

 considerably enhanced* by noticing that an emulsion of the 

 bacilli which were very motile of these colonies, subjected 

 to agglutination test with typhoid serum, gave a strikingly 

 positive test. When, after the method of Koch-Drigalski, a 

 loop of typhoid serum was added to several big drops of the 

 emulsion made by distributing a trace of such a blue 

 colony in sterile beef broth arrest of movement and agglo- 

 meration into large conspicuous clumps took place within a 

 a few minutes, the process of agglutination being quite 

 complete within five or six minutes. 



This occurred with quite a series of clean Whitstable 

 oysters, derived from Whitstable and from Langstone 

 channel. The difficulty and puzzle was, however, soon 

 solved, viz., these blue colonies appeared only after the 

 plates had been taken out of the hot incubator, i.e., at 

 37 C., and were then kept for several days either at 20 C., 

 or at the ordinary temperature of the laboratory. So long 

 as the plates had been kept in the hot incubator, i.e., at 

 37 C., there was no trace of these blue colonies, but they 

 gradually made their appearance after they had been kept 

 for several days at the lower temperature. 



Another fact noticed about these typhoid-like blue 

 colonies was this, that the bacilli composing them were thinner 

 than the B. typhosus and decidedly more cylindrical, and 

 even filamentous, but they showed active mobility just like 

 the B. typhosus. Sub-cultures in the different media estab- 



