CHAPTER XI. 
POND LIFE. 
Water full of life—Care required in dealing with it—The rotifera—Rules 
for cultivation—Nature's provision for young fish—Daphnia pulex—Cyclops quad- 
vicornis—Cypris tristriata—A rachnida— Notonecta—Corixa—Gammarus—Dytis- 
cus—Caddis worms —Ephemera—Shellfish—Parasites—Saprolegnia. 
\A\/HEN any important fish-cultural question requires to be 
answered, the safest and surest way of getting sound informa- 
tion on the subject is to send a thoroughly competent expert 
to make a careful examination into all the details of the case. 
This is the way to arrive at some really definite conclusion, and 
obtain a correct verdict. There are so many who are ready to 
denounce as hopeless anything that they themselves cannot 
understand or do, that if we listen to their cries nothing would 
ever be accomplished. Nearly every section of fish culture has 
its opponents, and but for the persevering efforts of a few 
individuals nothing would yet have been done towards cultivating 
the waters of the British Isles. 
The important subject to which I am in this chapter about 
briefly to allude, is one that is now engaging the attention of men 
of science, who have had their attention drawn to the great 
importance of its bearing on the welfare of our fisheries. At 
certain times of the year some of our waters are found to contain 
an enormous mass of living organisms, and we will now consider 
a few of these beings which inhabit our ponds and lakes, or their 
margins, with a view to the utilization or otherwise of the supply 
of fish food which Nature has already provided. 
The subject is an exceedingly wide one, and it is necessary 
at the outset to use caution in the course of our investigations, 
for we have not got very far before we find that we have enemies 
