1899] Moore, —Pollution of water-supplies by algae IOI 
other diatomes which possess a characteristic disagreeable taste, and 
numerous forms cause serious trouble in water that is to be used in 
the manufacture of paper. 
Perhaps the organism which produces the most unpleasant and 
disagreeable effect upon the various water-supplies in New England is 
Uroglena, a form which although claimed by zoólogists, has probably 
just as good a right to be studied by botanists. This occurs only 
during the colder months of the year, being most luxuriant when the 
water is covered with ice. In a very general way it may be said to 
resemble a volvox colony, that is, it consists of a gelatinous sphere in 
the periphery of which are embedded numerous green cells. These 
cells are each provided with a red spot and a pair of cilia of unequal 
length and these by their undulatory motion revolve the colony through 
the water with considerable rapidity. The pollution which Urog/ena 
produces is caused by an oil contained in the form of small globules in 
each cell. These cells are so delicate that the slightest change in the 
condition of the water is apt to bring about their disintegration and 
thus the oil is liberated, giving to the water a most disagreeable oily, 
fishy taste. This last season has been a particularly favorable one for 
Uroglena in Massachusetts, it. being especially troublesome at Hing- 
ham, and occurring at various other places. 
The question of how to prevent the appearance and growth of algae 
in water-supplies is, of course, an important one. While they can not 
be said to be actually injurious to health and there is no occasion for 
the alarm, which is sometimes aroused by newspaper articles, the in- 
convenience they cause is so considerable and the contaminated water 
so disagreeable that a practical means of removing them is much to be 
desired. ‘Thus far but little has been accomplished. It is known, of 
course, that the freer from organic matter a reservoir can be kept, the 
less likely it is to become infected by algae, and large sums of money 
are expended by water-boards in an effort to clean the ponds and 
reservoirs which furnish the supply of water. But when we consider 
that any good water contains all the elements necessary for the growth 
of these plants and that most of them have the power of forming rest- 
ing spores, which will tide them over unfavorable conditions and which 
can be carried great distances by the wind or other agencies, we see 
what a difficult problem the whole subject presents. By obtaining a 
sufficiently large number of statistics with regard to the exact condi- 
tions under which these organisms occur and by finding out through © 
