1897.] Biological Studies in Massachusetts. 579 
TABLE No. 1, 
Number of Genera. 
Classification. Common-| Occasion- | Common- | Occasion 
ly found jally found) ly found | ally ob- 
in lar, large small | served Total. 
numbers. | numbers. | numbers. 
Jiatomaceæ 5 4 4 92 35 
Chlorophycew. ...sesosesrees ee | 3 8 14 21 46 
Cyanophycee...... ...sseseeeee 4 oe 8 16 
Fungi 1 1 5 10 
q <hizopoda 0 0 4 6 
nfusoria 5 5 ) 20 39 
Rotifera 0 0 12 17 
rustac 0 0 ; 4 7 
Miscellaneous. ............... 0 0 ) 10 10 
Total 18 21 41 106 186 
rence, and their unpleasant effects. They are Asterionella, 
Anabaena, Clathrocystis, Coelosphaerium, Aphanizomenon, 
Oscillaria, Dinobryon, Peridinum, Synura, Uroglena and 
Glenodinuim. This list seems like a short one when one con- 
siders the annoyance that the micro-organisms have caused in 
the various water supplies of the State. 
The following tables, compiled from the examinations of the 
State Board of Health, serve to give one an idea of the distri- 
bution of the various classes of organisms in ground waters 
and surface waters. In most cases the numbers given are the 
averages of monthly examinations extending over one or 
more years. They were selected with a view to showing the 
greatest range in the number of organisms in the classes of 
water tabulated, and they illustrate in a striking manner the 
comparative absence of organisms (except Fungi) in springs, 
wells and filter galleries: the presence of a variety of organ- 
isms in small numbers in rivers, and the abundance of micro- 
scopic life in the more quiet waters of ponds and artificial 
reservoirs. It is only in waters of the latter class that the 
microscopical organisms occasion much trouble by their ex- 
cessive growth, and hereafter they alone will receive our con- 
sideration. 
