244 Ward. — Thames Bacteria , III. 
Plate. Extremely variable according to the conditions. The 
colonies begin as yellowish granular disks or ellipses. These grow out 
radially or at the ends into branched zoogloeas and fimbriated tufts, or 
may elongate into snake-like zoogloea-forms branching at the two 
ends : thus, according to conditions, there are formed in from two to 
four days, circular, dumb-bell-shaped, irregularly branched arachnoid 
or serpentine zoogloea-colonies, ochre-yellow in colour, and running 
into delicate filaments at the margins or ends, which ramify copiously 
(Figs. 54-57). To the unaided eye these colonies appear as delicate, 
mould-like, faintly iridescent growths, or as more obvious, ochre-yellow, 
somewhat zoned, oval or round colonies. At low temperatures, 
especially when the plates are exposed to light, the emerging colonies 
grow very slowly as thin, frondose, typhoid-like, irregular plates, 
marked with striae, and almost colourless, except at the thicker centre, 
where there is an irregular yellowish mass (Fig. 62): the submerged 
colonies under such conditions are dull yellow, very irregular in outline, 
and marked with constrictions. The mycelium-like, more delicate and 
branched form (Fig. 56) rapidly liquefies the gelatine completely in 
24-48 hours, the dumb-bell-shaped and zoned circular colonies 
(Fig. 55) only liquefy slowly and incompletely after four or five days. 
The frondose plates (Fig. 62) show no signs of liquefaction even after 
a week. 
Streak . At 15 0 C., an ochre-yellow, streaky and flecked growth is 
formed, which slowly liquefies the gelatine to a glairy fluid. In ten 
days half the tube is liquefied to a viscid fluid, in which a yellow deposit 
forms. 
Stab. In two days at 15 0 C.,a thistle-head funnel of liquefaction is 
formed, with greyish dots in the tunnel, and an ochre-yellow somewhat 
stellate mass floating on the liquid above. As the funnel approaches 
the sides of the tube and deepens (four to five days) the colonies in the 
tunnel show slightly yellow, and ochraceous flecks are deposited at the 
bottom of the liquefied gelatine above. In two to three weeks the 
gelatine is liquefied one-eighth down, a thick yellow deposit forming 
below the liquefied portion. (Fig. 58 ; cf. also Fig. 45.) 
Agar. In twenty-four hours at 20° C., the streak is yellow, with 
thin, glistening, frondose spreading margins, which are whiter and 
slightly iridescent. In three days (Fig. 59) the broad and more 
frondose expansion is a brighter ochre-yellow, thicker, glistening, with 
delicately fimbriated, thin, irregular, iridescent margins. 
