Ward . — Thames Bacteria , ///. 225 
be brought together as a group of allied varieties, or if you 
will, ‘ species.’ 
They all agree in forming the peculiar tenuous cloudy 
colonies on plates, composed of coarse and fine radiating and 
much interlaced tresses and filaments, like an extremely fine 
mycelium sunk in the gelatine. The coarser of these masses 
and tresses are in the condition of zoogloeas, i. e. the rods 
and filaments are held together by their swollen cell-walls. 
They also agree in liquefying the gelatine more or less 
rapidly. 
The filaments of which the tresses are composed are always 
very thin — about 0-5-0*75 11 — and break into rodlets about 
4 -6 ii long, which may again break up into shorter ones 1-2 /x 
long. These are either quiescent or only slightly motile, and 
no spores could be obtained in any cultures. 
Another point of general agreement is the gradual assump- 
tion of a more or less pronounced ochre-yellow to chrome- 
yellow colour in the older plate-cultures, and other gelatine 
cultures ; though, as we shall see, there is great variation as 
to the extent and depth of this. 
The growths on agar differ considerably in small details, 
but they agree in being more or less yellow, and in failing at 
temperatures above 25 0 C. 
On potato also, while great differences were observed as to 
the depth of colour and vigour of growth, all agree in forming 
some shade of yellow, and in refusing for the most part to 
grow above 25 0 C. 
In broth again, with differences in detail they agree in not 
growing above 25°, and in forming a shimmering turbidity 
and more or less yellow deposit. 
Similar resemblances in milk. No peptonization or, as 
a rule, marked coagulation occurs, but a faint acid reaction 
occurs in all. 
It is for these reasons that I propose to unite all these forms 
under a common type, which for further reasons which will 
come out as we proceed, I term the Yellow Proteus type. 
In order to make clear the details to follow, I begin with 
