THE SYSTEM OF ARTIFICIAL FLIES. 69 
' instead of on the surface; wet instead of dry; and in 
brisk motion up, down, or across stream, instead of pas- 
sively floating. No doubt if the flies could always be 
kept dry and passively floating—that is, as they are 
seen in nature—the exact imitation theory would (though 
only up to acertain point) be sound enough ; but as in 
practice this is impossible, we are perforce driven to arti- 
ficial expedients to extricate us from the “unnatural” 
dilemma. Thus at the very outset we find ourselves 
compelled to simulate life instead of death in our flies ; 
and for this purpose impart to them a wholly unnatural 
motion whilst swimming: again, because “ fluffy” mate- 
rials when wetted lose much of their strength of colour, 
fly bodies are constantly made of hard silk instead of soft 
dubbings ; and as it is found that a naturally propor- 
tioned insect is deficient in: “movement,” an unnatural 
quantity of legs (hackles) are added to it—in the 
smaller species the wings being often omitted en- 
tirely. In short, we are launched upon an altogether 
artificial system, in which experience must to a great 
extent supersede nature as a pilot. 
The colourists take advantage of this undeniable 
position to assail the whole system of “form” as a 
blunder, and in doing so themselves make a blunder still 
greater; they not only draw from correct premises an 
erroneous conclusion, but they draw a conclusion the 
very opposite of the logical one. For if it be admitted 
(a), that Trout do take the artificial for the natural fly, 
