BIOLOGICAL STUDY OF TAP WATER. 419 
‘eases are produced directly by these forms, it is quite proper that 
we should be very careful that the water we drink is free from them 
if possible. If we look for natural water however which is absolutely 
free from Bacteria, probably we shall look in vain. But we must 
remember that all forms of Bacteria are not capable of producing 
disease, even if some are, or at any rate that they do not do so under 
ordinary circumstances, but only in particular and well-marked con- 
ditions of the organism or organ attacked by them. We must not 
be surprised then to find Bacteria in our water supply. I have 
observed even in fresh filterings all the common forms, micrococci, 
rod-like forms, vibrios, spiral forms, and zooglaea stages. But if the 
filterings be allowed to stand exposed to the air for a few hours, it is 
amazing how rapidly they imcrease in numbers, and after a day or 
two the whole becomes converted into one mass of Bacteria in all 
stages, growing at the expense of the other organisms, and eventually 
leaving nothing but the siliceous frustules of Diatoms, and whatever 
other matter like this defies their digestive power. Probably there 
is no place where they thrive better, and where they exist in greater 
numbers, than in the School of Practical Science; for they are 
certain to be found there in everything which is not positively 
destructive to them. There is no doubt then that their presence in 
such abundance in sediment which has been allowed to stand for 
‘some time exposed may be in great measure accounted for by germs 
getting into it from the atmosphere, as well as those already there 
multiplying. 
Adopting the view held by Billroth, Nigeli, Cienkowski, Ray 
Lankester, and Zopf, that all the forms usually described under the 
generic names Micrococcus, Bacterium, Bacillus, Leptothrix, Clado- 
thrix, Vibrio, Spirillum, Spirochaete, &ec., are only development 
stages of Schizophytes, in opposition to that of Cohn and others, 
that they are distinct species without morphogenetic connection, all 
the forms observed have been referred to the two species, Cladothria 
dichotoma, Cohn, and Begyiatoa alba, Vauch. 
Concerning the first of these two Zopf remarks, that “what the 
common bread mould (Penicillium crustaceum) is among the aerial 
mould fungi, C’. dichotoma is among the aquatic fungi, and therefore 
it might be quite properly denominated the ‘ water-fungus’ (‘ Was- 
serpilz’) par excellence.” 
