SO 
we consider, sufficient to dispose of a general assumption 
that the predominating bacillus in an emulsion at the com- 
mencement of an experiment will, other things being equal, 
be the last to survive. 
Before finally leaving this subject we wish to emphasise, 
what has already been laid down, v7z., that we do not state 
that there is a perfectly fixed degree of power of resistance to 
sunlight in all specimens oi any one species, but simply, that 
a certain proportion of one organism resist sunlight longer 
than a certain proportion of another, both being placed under 
similar conditions. 
Making due allowance for the above mentioned objec- 
tions we consider that a few outstanding facts are apparent 
to any fair-minded individual. Of these perhaps the most 
important is the consistent rapid disappearance of coli com- 
munis. In support of this Experiments I and 2 are very con- 
vincing. In the first of these we start out with an enormous 
preponderance of these bacilli, and within a very short time 
they have disappeared, and it has become possible to isolate 
other varieties. Another equally interesting point is the 
tendency for the last organism to live being either one Grun- 
thal group or B. cloace. Practically all our experiments 
show that it is quite common for these varieties to survive 
all others. We are very anxious not to overestimate the 
value of these results, or to draw more conclusions from them 
than are legitimate, but the following broad conclusions 
appear to be justifiable :— 
(x) That the sun has a very powerful action in destroy- 
ing all fecal organisms in water, particularly when they are 
‘© naked ’’? and not surrounded by mucus derived from the 
intestine ; 
(2) That all feecal organisms do not possess the power 
of resisting the action of sunlight to an equal degree ; 
(3) That it is possible to divide fecal organisms, with 
a reasonable degree of accuracy, into the following classes :— 
(i) The delicate organisms or those that are very sus- 
ceptible to the action of the sunlight (vide the 
remarks on coli communis) ; 
