186 EVOLUTION AND DISEASE. 
degrees may be met with, from a broad web to others ing 
which the rachis of the tail feathers is clean from the first. — 
FIG. 99.—Tail of a normal Trout for comparison. (After 
Traquair.) 
The second case is furnished by the so-called tailless 
trout of Islay. Professor Traquair has published an 
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