假捏虛言 A Deposition in False Words
好大聖，假捏虛言，對眾供道：好大圣，假捏虚言，对众供道：
逐句解 Line by line
Excellent Great Sage! He framed a false tale and deposed before the company:
供 is gòng again, and 對眾供道 is the formula for testimony given in open court. 假捏虛言 tells us in advance that every word of what follows is invention — which turns out to be a joke, since every word of it is also true of a crab.
"Born in a lake, I make my living there; beside the cliff I dig my hole and lodge as I may."
為 is wéi, the copular reading. 傍 is páng, beside. 權居 is to lodge provisionally, and it sets the humble note the whole deposition keeps.
"Because the days have been long I have come to some ease of body, and hold office as a Sidling Gentleman-at-Arms."
The pun, cashed. 橫行介士 — sidling gentleman-at-arms — is an old kenning for a crab, a creature that walks crosswise and wears armour, but it is cast here as an official title. So the prisoner answers the charge of 橫行 by claiming it is a rank he was awarded. 介 is the shell and also the mail of a man-at-arms. 得 is dé, attainment.
"Treading the weeds and trailing the mud, a shabby thing, I have never learned the forms of conduct."
落索 is dispirited, shabby, at a loose end. 行儀 is deportment — the very thing the old dragon has charged him with lacking, now conceded before it can be pressed.
"Not knowing the statutes I have affronted the royal majesty. Prostrate I beg your honoured mercy to forgive the offence!"
度 is dù, a statute or measure. 伏望 is the formula of a petition submitted face to the ground, and it closes the deposition in the register of a memorial to the throne.
The deposition is a lyric set to the tune 西江月, and the metre is exact — six, six, seven, six in each half. It is the only verse in the chapter written to a named tune; the chapter's eight other set-pieces are in the freer rhapsody manner. That a crab under arrest should answer a capital charge in a strict lyric form is the joke, and the novel does not comment on it.
The defence is a small masterpiece of forensic wriggling, and it turns entirely on the word the old dragon used to accuse him. Charged with 橫行 — going crosswise, behaving lawlessly — the Great Sage replies that he holds office as a 橫行介士, a sidling gentleman-at-arms. The offence is reclassified as a rank. He then pleads provincial ignorance: a creature that lodges in a hole beside a cliff, treads weeds and trails mud, has never had occasion to learn court manners.
Every line of it is true of a crab and false of the speaker, which is what makes it unanswerable. He was born in water, he does live under a bank, he does walk sideways and wear a shell, and he does not know the etiquette of a dragon palace. We were told at the head of the passage that this is a fabrication. The fabrication consists of nothing but accurate natural history.