508 The American Naturalist. [June, 
what longer intervals samples for bacteriological examination 
are collected from the brooks in the more thickly settled por- 
tions of the watershed and from the various filter beds. Sam- 
ples from beneath the surface of the reservoirs are collected 
in sterilized vacuum tubes, lowered to position in heavy lead 
tubes; the seal is broken by an arrangement of spring and 
flexible cord in a manner similar to that described above. On 
account of the uncertainty which surrounds the methods of 
bacteriology at the present day comparatively little of the 
bacteriological work has been published. 
4. Photomicrographical—For some time after the establish- 
ment of the laboratory much attention was given to the subject 
of photography, and excellent photomicrographs of most of the 
important organisms have been secured. Of late the time re- 
quired for this work has been given over to the more important 
bacteriological investigations. 
5. Experimental—In addition to the routine work many 
experiments of a practical and scientific nature have been 
carried on. Of the subjects investigated the following may be 
given as illustrations: The cause of the seasonal distribution 
of the various classes of organisms. The effect of temperature, 
light and air upon the growth of diatoms. The cause and 
extent of the taste produced in water by organisms. The effect 
of swamps upon the quality of a water supply. A study of 
“stagnation phenomena” in a deep pond. The bleaching ac- 
tion of sunlight. The efficiency of sand and mechanical filtra- 
tion in the purification of water. 
Comparatively little chemical work is done in the laboratory, 
as this branch of the subject is deemed sufficiently treated in 
the monthly examinations of the State Board of Health. 
Taken together, all the biological work of the character de- 
scribed that has been done in Massachusetts during the past 
ten years is of great value from a purely scientific as well as 
from a sanitary standpoint; and the increasing importance of 
the subject and the growing interest in limnological studies in 
other countries make it desirable that this work should be 
better known. It is the intention to bring together in this 
series of articles an outline of the work done, and some of the 
most important of the results obtained, treating the subject 
not so much from a sanitary as from a biological point of view. 
