MEMOIRS OP THE NATIONAL ACADEMY OF SCIENCES. 457 



The (lutliiie is sharply defined, wii\'y, and irregular; toward the center a browiiisli yellow color 

 appears, and a sharply defined, yellow-brown refractive central nucleus may be observed. Tlie 

 colony soon becomes denser and grayish white throngliout, and sinks into the gelatin, which is 

 slowly liquclied. The deep colonies, under a low niagiiilying power, are i-ounded or slightly 

 irregular in outline and sharply defined; they are slightly granular and of a brownish yellow 

 tint, often darker toward the center. A dark ring may sometimes be observed between the 

 center and the periplierj*. 



Gelatin slant.— A smooth, gray-white stripe with wavy margins is formed at first; this sinks 

 into the gelatin, and a furrow is formed lined by a grayish white, viscid layer; lifxuefactioii slowly 

 occurs and the growth to some extent gradually slips downward; the surface of the nonliquefied 

 gelatin acquires a hazy appearance. 



Gelatin Utah — A thin, grayish white surface expansion with irregular outlines is formed; this 

 slowly sinks into the gelatin, which is slowly liquefied ; there is a fair growth along the line of 

 inoculation of brownish gray, discrete, and confluent colonies. 



Acid gelatin. — The growth is perhaps less vigorous. 



Agar slant. — Whitish, semitransluceut, shining growth, not widely spreading; the agar after 

 a time acquires a slight green tint. 



Bouillon. — Clouded; whitish flocculi may form an imjierfect pellicle on the surface; there is a. 

 whitish sediment, and the bouillon may acquire a slight green tint. 



Potato. — Brownish, viscid, rather thick growth, spreading rather widely and becoming darker 

 in older cultures. 



Litmus viill: — Decolorized; after a few weeks there is a smoky bluish layer at the top, while 

 below this the milk has a brownish white color; there may form a tough membrane on the surface 

 which permits the tube to be inverted without disturbing the liqnid; above this there is a bluish 

 ring on the tube wall; there is no coagulation, but the milk may be viscid in old cultures; the. 

 reaction is alkaline. 



Sugar gelatin in deep stab. — No growth. 



Rosolic acid. — Rose color much deepened. 



Indol production. — Faint reaction; no nitrite production. 



Relation to temperature. — Does not grow at 35° to 30° C. 



Bacillus duplicatus. 



(Variety a.) 



Isolated from the water of the Schuylkill River. A medium-sized, rather short, motile bacillus 

 with rounded ends, occuring singly, in pairs, and in threads; it has a terminal flagellum; no spore 

 formation observed. 



Colonics in gelatin. — On the second day the surface colonies appear as gray, white, translucent, 

 shining, slightly elevated disks 1 mm. to 2 mm. in diameter, with smooth or slightly irregular rounded 

 outlines, sharply defined. Under a low magnifying power the colony is of a dark brownish color 

 toward the center, but becoming translucent and colorless toward the margin ; the outline is smooth 

 or slightly wavy, and is sharply defined; near the center a brownish or bi'ownish green nucleus is 

 seen, and between this and the periphery indistinct, radiating, brownish lines maybe observed. 

 As development iJroceeds the colony, as observed with the low magnifying power, becomes darker 

 and more opaque from the center to the i)eriphery, and a greenish shimmer appears; near the 

 margin, which remains thin and translucent, a brownish mottling may be seen. The deep colonies 

 under the low power are rounded, dark, granular, somewhat refracting, brown or brownish green 

 at the center, and have a smooth, sharply defined outline. About the third day the colony becomes 

 denser, slightly greenish white in color-, sinks slightly into the gelatin, and li(iuefaction slowly 

 occurs; the gelatin may become slightly green, fluorescent; somefimes one or two thick, club- 

 shaped processes may be seeli extending into the gelatin from the under surface of the colony. 



Gelatin stab. — Liquefaction in dcej) saucer form, constricted at the top and extending to the 

 tube wall in about a week, and slowly downward; the flow of the liquefaction, after the tube 

 wall has been reached, becomes level. (See fig. 21. o) On the surface there is a very thin, almost 



