12 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



the third or fourth day, and becomes cream colored. The folds soften down, or are overgrown in 

 a few days, and the layer becomes a shiny looking dirty cream or putty color. It has a strong 

 musty odor, like stale milk. 



Bouillon. — Becomes diffusely clouded in thirty-six hours, and has large white flocculi floating 

 in it. These settle to the bottom, forming a dense whitish deposit, while the bouillon remains 

 almost entirely clear. 



Litmus milk. — The milk becomes stratified, being lightest at the bottom, and somewhat 

 reddish at the top, where it is watery and translucent. The color is discharged slowly and the 

 casein apparently dissolved. Reaction neutral. In some cultures the milk becomes more blue, 

 and after a time, a beautiful violet color by transmitted light, with a decidedly alkaline reaction, 

 the casein being dissolved. 



Sugar gelatin, deep stub. — Growth the same as in plain, but liquefaction takes place much more 

 rapidly. No gas is produced. 



Rosolic acid. — No change in color is noticed. 



Indol. — Reaction negative. 



Relation to temperature. — Grows somewhat more rapidly at .'^5° to 36° C. 



Note. — The above description differs from those found in most books in some respects. I have 

 found considerable differences in different cultures of Megatherium, and cultures recently obtained 

 from the earth behave differently than when kept on artificial culture media for some time. As 

 Friinkel says, " It seems almost as if a continued nutrition with our usual food media did not 

 agree with this mocroorgauism." And speakiug of the appearance of the rods he says, 

 "and one might be tempted to suppose that a new variety had arisen, were it not always easy to 

 breed normal cells again from these monstrous and crippled forms by employing a more suitable 

 culture medium." (Textbook of Bacteriology, American edition.) 



I have found this true as regards the cells themselves, but the growth in the different media 

 is never quite the same as when the cultures are fresh from the soil, so much so that it is often 

 hard to believe that one has the same organism. 



BACILLI'S FORMOSUS. 



(Figs. 6 ami 7, PI. I.) 



Found in made soil a number of years old. 



Character.— Requires oxygen for good development, but shows some growth in an atmosphere 

 of hydrogen. 



Morphology. — Slender, straight rods, with rounded ends, from seven to eleven times as long 

 as broad. Occurs singly and in twos and threes. 



Motility. — Slight independent movements noticed. 



Flagella not demonstrated. 



Spore formation doubtful. Probably does not form spores. 



Colonies on gelatin 2>lates. — Colonies are seen in twenty-four to twenty-eight hours as minute 

 greeuish-white dots. At the end of thirty-six hours the deep are still punctiform, while those on 

 the surface are one-fourth of a millimeter in diameter, x 80. The deep are yellowish disks, with 

 even edges and finely granular contents. The surfaces are circular, have even edges, and are 

 yellowish in the center, fading to gray at the edges. They are finely granular, with no distinctive 

 features. At the end of sixty hours the deep colonies are yellowish dots, while on the surface 

 they are white, and one-half of a millimeter in diameter, x 80. Deep show no change. On the 

 surface the colonies are made up of a nucleus, more or less distinct in the different colonics and 

 yellowish brown in color. Around this is a zone of lighter yellowish hue, traversed by brownish 

 wavy lines. Beyond is a zone of much darker color, and fading into pale yellow at the margins. 

 It is made up of lines radially disposed, with here and there cloudy masses of brownish granules. 

 The edges are regular and smooth. At the end of a week the surface colonies are about 1 nun. 

 in diameter, x 80. Many still show a nucleus, and the zones above described. In the majority 

 the nucleus and zone next to it have become of the same color, and merge into a dark-brown 

 zone, which fades into a lighter marginal zone. In all the colonies, numbers of amorphous 



