Mar. 24. 1919 Ammonification of Manure in Soil 343 



It is about 0.2 ju in diameter. Its length is ordinarily about 2 /i, but, 

 as stated by Wright, longer forms occur. These rods stain solid with 

 the ordinary bacterial stains, such as fuchsin or methylene blue; but with 

 the more delicate dye, rose Bengal, they appear to be made up of tiny 

 granules. Cultures a few days old are sometimes made up wholly of 

 these granules, each about 0.2 ju in diameter. Such a preparation looks 

 like a very tiny micrococcus. Cultures of this sort have proved to be alive 

 upon transfer to fresh media, but v/hether the granules are capable of 

 growth or whether the multiplication is carried on by a few stray rods 

 present in too small numbers to be observed under the microscope is still 

 an unanswered question. This suggests very strongly Lohnis and Smith's 

 idea (55) as to life cycles among bacteria, but as yet it has not proved 

 possible to find whether that is the true explanation of this case. The 

 granules may be degenerate forms, a possibility suggested by the rapidity 

 with which cultures die, or the organism may be actually a coccus 

 that has a tendency to produce short chains or filaments in young cultures. 



The majority of the cultures show no motility, although occasionally 

 one is observed that is distinctly motile. This undoubtedly explains 

 why Wright (55) called the organism immotile. An idea of the diffi- 

 culty in studying motility can be obtained from the trouble encountered 

 in demonstrating flagella on the strain used in Bright's work. This strain 

 was kept under observation for a few months without observing any 

 motility, when at last, quite unexpectedly, a distinctly motile culture of 

 it was obtained. On the same day two other strains, previously showing 

 no motility, were found to be motile. No apparent reason could be 

 found for this sudden development of motility, which persisted through 

 at least three or four generations. Meanwhile flagella preparations were 

 made from the strain used by Bright in the work reported above, and 

 one or two organisms were observed with a single flagellum each. This 

 flagellum is rather long in comparison to the length of the rod. This 

 finding agrees with previous studies of this organism made by the writer. 

 Three strains in all have been successfully stained, and about 10 differ- 

 ent organisms have been observed with a single polar flagellum each. 

 Preparations were always too poor to allow photomicrographs, but there 

 seems to be sufficient evidence to establish the presence of one polar 

 flagellum. For this reason Wright's name, "Bacillus catidatus," is 

 changed to Pseudomonas caudatus. 



Chromogenesis. — Next to its morphology, pigment production is 

 the most striking characteristic of Ps. caudatus. The pigment grades 

 from yellow to orange. On potato and gelatin it is generally distinctly 

 orange, while on beef -extract peptone agar it is more of a yellow. Its 

 color on the latter medium is practically the same as that v^^hich is typical 

 of the orange pyogenic cocci, designated cadmium-orange by Winslow 

 and Winslow (52) in their book on the Coccaceae. The typical color, 

 indeed, is exactly the shade of cadmium -orange which the Winslows 



