Juny 16, 1897.] 
If anything be evolved by evolution it is 
evident that, whatever its nature may be, it 
must cease to be evolved if it would main- 
tain its integrity. For inertia of matter 
and conservation of force apply to bodies 
which no longer are undergoing evolution , 
Variation, asa process of becoming different, 
is a, characteristic of living bodies, and, 
though it is not doubted that in the pheno- 
mena of variation it is ordinary chemical 
and physical matter which exhibits the 
peculiar vital phenomena, we have no reason 
to suppose that the operations of physics 
and chemistry are thus variable. 
H. S. WIL1LrAMs. 
YALE UNIVERSITY. 
WICROSCOPICAL EXAMINATION OF WATER, 
WITH A DESCRIPTION OF A SIMPLE 
FORM OF APPARATUS. 
THE microscopical examination of water 
is becoming every year a matter of greater 
interest, and the study of the minute 
aquatic plants and animals is more and 
more attracting the attention of scientists. 
These organisms are interesting for several 
reasons and, besides recognizing their im- 
portance in the domain of pure science, 
we are beginning to appreciate the great 
part that they play in nature and their 
effect, direct and indirect, upon the human 
being. Their presence in surface waters is 
often the cause of much harm when the 
water is used for purposes of domestic sup- 
ply ; scores of instances may be mentioned 
where they have rendered the water en- 
tirely unfit for use. On the other hand, 
their presence in ponds and streams is of 
importance to the fish-culturist because 
they form the fundamental source of the 
food supply of fishes; this is probably true 
both of salt and fresh water. 
Because of this connection between the 
number of microscopical organisms in a 
cubic centimeter of water and the price of 
fish in our markets, the study of the 
SCIENCE. 
89 
‘plankton,’ 7%. e¢., the floating micro-or- 
ganisms, is being emphasized on both 
sides of the Atlantic. Observers are be- 
ginning to trace the connection between 
the presence of microscopical organisms 
and the abundance of fish in our lakes, and 
valuable comparisons have been made be- 
tween the stomach and intestinal contents 
of fishes and the organisms found in the 
water where the catches were made. This 
work is of very great importance and 
should be vigorously pursued by our fish 
commissions. To be of the greatest value 
it should extend well over the country and 
include lakes and ponds sufficiently differ- 
ent in character to enable one to determine 
the laws governing the nature and distribu- 
tion of the plankton in various climates 
and under various conditions. The study 
ought not to be carried on spasmodically, 
as, for instance, during the short vacation 
of some college professor who generously 
gives his time and talents to the cause, but 
should be undertaken seriously and con- 
tinued throughout the whole year. Only 
in this way can we obtain the data neces- 
sary for a complete understanding of the 
subject. 
Since water works managers are equally 
interested in the microscopical organisms 
found in surface waters, and up to the 
present time have been responsible for most 
of the work done upon the subject, it might 
be possible for fish commissions, boards of 
health, water-works superintendents, and 
others interested, to work together accord- 
ing to a definite concerted plan, sending 
their results to some central commission or 
committee for comparison and study. Such 
an extended biological study taken in con- 
nection with meteorological records and 
observations upon the temperature, trans- 
parency, etc., of the water would be of very 
great value. And it would seem that we 
have little excuse for neglecting to cultivate 
this fruitful field of research. Vast num- 
