296. THE MIcROSCOPE. 
to find them, If you want certain Polyzoa, these are the best 
of good places to find them ; but for Infusoria go elsewhere. 
A shallow pool whose bottom is covered with last year’s dead 
leaves is commonly well supplied with free swimming animals, 
and some of the bottom should be scooped up in the tin dipper 
and taken home to the aquarium. Any pond whose surface 
bears much Lemna is also the haunt of many of the free swim- 
ming Infusoria. The most prolific places are those little ponds 
fed by springs at the bottom, or filled by freshets from a creek 
or other stream and for the rest of the year land-locked, shaded 
by trees and bushes, protected from too rapid evaporation by a 
coating of Lemna fronds, and filled with Nuphar (Candock), and 
Ceratophyllum, and perhaps Myriophyllum, although it is not very 
common in such places. The shade should not be too dense, 
nor the sun-shine on the surface too bright; the proper con- 
ditions can be learned only by experience and experiment. In 
such a pond the free swimming Infusoria will abound, or its 
water will prove prolific if kept in the small aquarium. These 
are the places tuo for Chxtonotus. 
Those temporary pools so often found by the side of country 
paths in the early spring, formed by the warm rain collected in 
little hollows where the leaves have lain all winter, and which 
dry away almost before the new leaves have sought the sun, 
those shallow little lakelets are often wondrously rich in forms 
not to be found elsewhere at any other time of the year. They 
should never be passed without a dip. While the surface is still 
filmed with ice such water may teem with animal life, just such 
life as the microscopist wants. 
It is not possible to point out the exact locality where an 
abundance of microscopic animals may be found. They appear 
a law to themselves. The pond that may seem a likely place, 
may for some unknown reason be barren; while another to all 
appearance worthless may prove of great value. The food sup- 
ply may be the cause, or the temperature, or freedom from ene- 
mies, or some other thing. The microscopist can only take his 
dips to the instrument, hoping he has the success he has wished 
for. 
There is one place however to which he need never go. This 
is the thick mud at the bottom. Here some Rhizopodia may be 
collected, but Infusoria and other creatures rarely. They prefer 
