Head like a snake,
Neck like a drake,
Side like a bream,
Back like a beam,
Tail like a rat,
Foot like a cat.
Speaking from personal experience, he adds, "I can tell you, as the owner of a greyhound, that the similes of this riddle are very accurate." It "does what almost all good riddles do—it explodes for a moment our habitual classifications of phenomena."
He deconstructs the process:
Not only does a riddle offer us, once we have solved it, a yoking of supposedly unrelated things; it obliges us, in the process of solution, to strike out across the conceptual grid which our minds have imposed upon the world. If an enigma seems to turn upon the word head, for example, we find ourselves ransacking the environment for things and creatures to which it might apply: a man, a river, a pin, a bed, a glass of beer, a boil, a parade, a daisy."
He is always insightful, and—to be fair—he goes out of his way to mention that these are not to be considered finished, polished essays (though some are). They are incidental pieces. For me, the only limiting factor in my appreciation of the book, depends on the extent of my interest in the subject at hand: my interests are not identical to his, and often his speculations wander off into topics that I am not keen to study. Even the "Riddles" is a case in point.
Riddles can be interesting and fun—but as in the case of the Agatha Christie play I just saw, after the murderer has been revealed (the last person you would expect), my reaction is, "How clever, she did that very well, ho hum." A riddle such as the above is concise, whereas a detective mystery is drawn out; this pertains to language and perception, while, if that may too, it carries a lot more baggage.
The riddle, even as Wilbur's exploration of it, is more sophisticated than a murder puzzle in detective fiction, yet they belong to the same order.