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 



Fig. 1. — Melosira dentata, n. sp., filament of 4 frustules. 



Fig-. 2. — Qlosterium, sp. ? 



Fig. 3. — Clos. filiforme, n. sp. 



Fig. 4. — Unknown form — probably a Desmid. 



Figs. 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. 



