418 BIOLOGICAL STUDY OF TAP WATER. 
Other Chlorophyllaceous Algae present were Protococcus sp. ? 
Chlorococcus sp.? diam. of cell itself being 0°0176 mm., and of 
ell together with its hyaline coat 0°0264 mm. Ankistrodesmus 
(Rhaphidium) falcatus, Scenedesmus quadricauda, Pediastrum sp. ? 
Pediastrum Boryanum. The forms included in this latter species 
vary somewhat from the description given by Rabenhorst and Archer. 
The coenobium is circular in outline, cells in a single stratum, 
arranged in three rows round a central cell (1 + 4 + 10 + 15); 
inner cells variable, 4-6 angled, concave at one side ; peripheral cells 
‘convex on the inner side, on the outer side notched and tapering into 
two long subulate points. Diam. of peripheral cells 0-0065 mm. 
( = about 950”). 
I have also seen another species of Pediastrum which is not 
described in any work to which I have had access. The cells are in 
a Single stratum, and in two rows round a central cell (1 + 6 + 12); 
inner cells polyhedral, 4—6 angled; peripheral cells pentagonal ; 
external angle produced into a single process about as long as the 
diameter of the cell. Diam. of coenobium 0:0434 mm. ( =0-00173"), 
and of peripheral cells 0-°0124 mm. ( = 0-0005”). 
Spirogyra sp.? Sterile joints 10 times as long as broad; spiral 
single with 4 turns; cell wall at each end produced. Diam. 0-0124 
mm. ( = 00005"). Fertile joints not observed. 
PHYCOCHROMACEAE. 
Belonging to the Phycochroms there were a few forms observed, 
Viz. :-— 
Gleocapsa sparsa, which is probably only a zooglaea stage of 
Sirosiphon ; Merismopedia novu (sp. ?); and at least two species of 
Oscillaria, which have been referred to Os. nigra, Vauch, and Os. 
chlorina, Kiitzing, the former being quite common during the month 
of March, more so probably than at any other time. 
SCHIZOPHYTAE. 
Under the name Schizophytes are included all the organisms com- 
monly known as Bacteria, together with a few parallel green forms, 
multiplying chiefly by transverse fission, though in some cases spores 
are formed. These organisms at best have but a doubtful reputation ; 
and if Intermittent and other malarial fevers, Anthrax, Diphtheria, 
Septicaemia, Pyaemia, Tubercle, and other virulent contagious dis- 
