[jONEs] STUDY OF SOME AZOTOBACTER 49 



and occasionally threes. The internal protoplasm is mostly homo- 

 geneous; occasionally, however, a spherical body which may be nuclear 

 in character is present, and when fission of the cell occurs fission of 

 this body usually takes place also, but not always, see PL IV, Figs. 

 1 and 2. After four days, many of the cells gradually become coarsely 

 granular, being filled with spherical granules. See PI. IV, Figs. 6 and 8. 

 These granules are of at least two kinds. The one kind which pre- 

 dominates gives the golden brown coloration of the glycogen reaction 

 when treated with iodine-potas-iodide solution, but is not stained with 

 the anilin dyes. The other kind of granule, which, by the way, does 

 not always appear to be present, does not give the glycogen reaction 

 but does stain with various of the anilin dyes. At this stage in actively 

 growing cultures many of the organisms disintegrate, the granules 

 bursting from the enveloping membrane. The scattered granules of 

 the number one type which give the glycogen reaction slowly disappear, 

 whilst those of the second type begin to grow and multiply by fission. 

 They are sometimes motile and delicate flagella have been observed on 

 them. See PI. V, Figs. 9, 10, 11, 12. From their staining reactions, 

 it would appear as though they were of the same substance as the 

 aforementioned supposed nuclear body. In cultures of A^ and Aj 

 after about three days, the organisms produce large soft capsules. 

 At first these capsules are negative to certain aniline dyes, whilst the 

 organism within is positive. Later, however, this order is reversed, 

 the capsule becoming positive and the organism negative. The capsule 

 is never positive to the glycogen reaction but the organism is always 

 so, though when young only slightly, giving a stronger reaction as age 

 increases. Fission may occur a limited number of times within the 

 capsule, thus giving within a capsule a cluster of organisms varying in 

 number from two to six or eight, usually adhering together in more or 

 less irregular groups. See PI. II, Figs. 4, 5, 6; and PI. Ill, Fig. 2. 

 The capsular material, being positive to the stain, forms a dark back- 

 ground for the organisms, many of which are at this stage negative to 

 the stain. As the culture ages, the capsules appear to merge together 

 into a common slimy matrix from which the organisms become more 

 or less readily detached when smears are made for staining purposes. 

 In cultures of A3, capsules are but little in evidence, and in cultures 

 of A4 they are not present at all. These organisms in cultures of from 

 four to ten days old are more granular than are those of A^ and Aj, 

 and not being enveloped in capsules they disintegrate more readily, 

 so that if at this stage smear stains are made, granular organisms in 

 all stages of disintegration are observed, also many loose granules 

 some positive and some negative to the stain. See PL III, Figs. 5 

 and 8. In cultures that are three weeks old and older, whilst we may 



