342 A Soil Bacillus of the Type of De Bary's B. megatherium. 



germinates at one end in a direction parallel to the longer axis. The 

 subsequent growth of the chains is intercalary as well as terminal. 

 The rate of growth was obtained by taking consecutive measurements 

 of vigorous rods or chains, and noting the time required for the original 

 length to double. This time, according to the terminology suggested 

 by Marshall Ward, is known as the " doubling period." In this case 

 the doubling period in saccharose-broth at 22'5 C. is forty-eight minutes, 

 at 19-5 20-5 C., 120 minutes. The slow growth of this organism at 

 these temperatures, and its sensitiveness to slight changes of tempera- 

 ture, are well illustrated by these and similar observations. 



When united in long chains the organism is non-motile, but rods 

 and short chains freshly produced from spores or involution-forms in 

 liquid media exhibit active motility, especially at temperatures between 

 23 C. and 33 C. This consists of progressive, undulating, and 

 rotary motions, and may last for several hours. It is confined to 

 isolated rods, and to chains of not more than three to six individuals. 

 Progressive motion is never observable in chains of more than three 

 united rods. 



Involution-forms are produced commonly in old cultures, or in 

 cultures made at low temperatures. They consist of enormously 

 swollen, fusiform, or drum-stick bodies, the contents of which are com- 

 posed of coarsely granular cytoplasm and numbers of oily globules. 

 In some cases the cytoplasm is found to have undergone plasmolysis, 

 but if this has not gone too far, the involution forms are able to 

 develop into normal rods if transferred to a suitable environment. 

 The organism is non-pathogenic, produces no pigment or evolution of 

 gas, and stains readily with carbol-fuchsine, aniline-gentian-violet, or by 

 Gram's method. 



In conclusion it may be said that this bacillus presents many points 

 of resemblance to certain well-known species, but at present it may be 

 impossible to refer it accurately. From B. aerophilus, Lib., it is 

 distinguished by its facultative anaerobism, its colour, its mode of lique- 

 faction, &c. ; from B. stibtilis, Ehr., B. vulgatus (Fliigge), Mig., and 

 B. mesentericus (Fliigge), Lehm. and Neum., by various minor characters. 

 The description of Russell's B. granulosus is not sufficiently detailed to 

 make an accurate comparison possible. That it is closely allied to 

 De Bary's B. megatherium is very evident, and it is quite possible that 

 prolonged investigation of the two forms side by side may prove them 

 to be identical. In that case added interest will attach to my investiga- 

 tions, in the way of showing the remarkable variations which may be 

 produced within the limits of a single species, by different methods of 

 treatment, De Bary's form being nearly twice as thick as this one. 



