190 OUTLINES OF BACTERIOLOGY 



kind of movement (Fig. 116). When the motile individuals come 

 to rest they collect together to form irregular angular colonies, which 

 gradually collect to form the Zoogloeae. A variety isolated from 

 Tokio (Japan) was also found to exhibit the same characteristics 

 as the above varieties, and with the exception of small differences 



Fio. 115. Zoogloea of nitrite- FIG. 116. Nitrite-bacteria. (Java.) 



bacteria. Free-swimming individuals. 



with regard to the size of the individuals and of the Zoogloeae, 

 the same can be said of the varieties obtained from Algiers and Tunis 

 (North Africa). 



The greatest deviation from the other varieties was found in a 

 nitrite microbe which was isolated from Quito (South America). In 

 this variety the individuals are round, being about 1'5-1'7/x in 

 diameter, and are remarkable in never passing over into the Zoogloea 

 condition, always remaining free and motile. On silicon jelly rela- 

 tively large colonies are formed, each of which has the appearance 

 of a drop of turbid, yellowish liquid. -Closely related to the Quito 

 variety is one isolated from Brazil, though the individuals of the 

 latter are larger, extending to about 2 /x or more. Finally, an 

 Australian variety has been examined arid found to agree with the 

 South American varieties in almost all particulars, the chief differ- 

 ence being the smallness of the individuals of the Australian 

 variety. 



Although a good deal still remains to be done with regard to the 

 differences and similarities of the various varieties of the nitrite- 

 bacteria, as seen from the above account, all are very closely con- 

 nected, and it seems probable that all have been derived originally 

 from a single species, that has spread itself practically over the 

 whole globe. 



