266 Pr.ofs. Percy Frankland and Marshall Ward. 



I have now, after long and careful studies of its behaviour on 

 different media, and in various circumstances, little hesitation in 

 referring this species to Fraenkel's Bacillus ramosus, the form com- 

 monly known as the Wurzel-bacillus in Germany, but which passes 

 under various names, and concerning which there is still a good deal 

 of confusion in the various text-books and bacterial floras which 

 mention it. 



I shall discuss these matters and the synonymy at the end of the 

 present section of the paper ; but since I have succeeded in following 

 out the life-history of this species in a singularly complete manner, 

 and find the organism a remarkably typical and instructive one, it 

 has seemed worth while to give in detail all the facts which have 

 come under my observation, and especially to call the reader's atten- 

 tion to the fact that it runs through its entire life-history, from spore 

 to spore-formation, in from thirty to sixty hours at ordinary tempera- 

 tures,* and that I have been enabled to follow the course of this life- 

 history by continuous observations under powers (l/12th and l/20th 

 oil-immersions) much higher than have commonly been successfully 

 employed for such observations. 



Bacteriological Cultures. 



In the preliminary plate-cultures in 10 per cent, gelatine, made to 

 isolate it from the Thames water, the colonies look so like the 

 mycelium of a fine white mould fungus, that, as said, it is quite con- 

 ceivable they might be overlooked or neglected by observers not 

 sufficiently on their guard concerning such deceptive forms. In fig. 1 

 is represented one of these colonies, natural size, as seen on the second 

 day, at 35 C. From a darker centre, which already shows signs of 

 softening and liquefying the gelatine, wavy strands, of varying 

 diameters, radiate outwards, and break up into finer and finer strands 

 or filaments, until they fade'away imperceptibly at the margins. The 

 whole of this circular colony has a milky-white, somewhat opaque 

 appearance, especially in the denser centre, which may have a 

 yellowish tinge now or a little later ; as we approach the indistinct 

 margins, the opacity gradually gives way to a translucency, and 

 eventually transparency, which prevent sharp demarcation from the 

 gelatine around. 



In a recorded series of observations of such colonies, at 15 C., I 

 found they were first visible to the unaided eye in about forty to 

 forty-eight hours; in seventy-two hours the average diameter was 

 25 mm. ; in ninety-six hours about 50 mm. ; and in six days (164 

 hours) a single colony covered nearly half the area of a Petri dish. 



* The ease with which it can be obtained and grown suggests that this species 

 would be a much better typelfor teaching! purposes than the smaller . subtilis- 

 commonly used. 



