426 BIOLOGICAL STUDY OF TAP WATER. 
and I have found it necessary to run the tap a considerable time to 
collect any appreciable quantity. 
As already stated, my investigations have been confined to the 
tap water in the School of Practical Science ; and, while admitting 
that other taps in different parts of the city would probably give 
different results as to quantity, yet I think the quality would be 
found to be practically the same. 
APRIL 7th, 1883. 
EXPLANATION OF THE FIGURES IN PLATE. 
Fie. 1.-—Melosira dentata, n. sp., filament of 4 frustules. 
Fie. 2.—Closterium, sp. ? 
Fic. 3.—Clos. jiliforme, n. sp. 
Fie. 4.—Unknown form—probably a Desmid. 
Fies. 5, 6.—Encysted forms of Dinobryon sertularia, Ehr. 
Fig. 7.—Flagellate Infusorian allied to Bicosoeca lacustris, J. Clark, and 
Stylobryon petiolatum, Duj.; e, eye-spot ; cv, contractile vacuole ; 
lb, lateral bands. 
EO 
