坐在籠中 Some Played And Some Were Crying
有的坐在籠中頑耍，有的坐在裡邊啼哭；有的吃果子，有的或睡坐。行者看罷，現原身，回報唐僧道：「那籠裡是些小孩子，大者不滿七歲，小者只有五歲，不知何故。」三藏見說，疑思不定。有的坐在笼中顽耍，有的坐在里边啼哭；有的吃果子，有的或睡坐。行者看罢，现原身，回报唐僧道：「那笼里是些小孩子，大者不满七岁，小者只有五岁，不知何故。」三藏见说，疑思不定。
逐句解 Line by line
Some sat in the coops playing, some sat inside crying; some were eating fruit, and some were dozing where they sat.
Four clauses on one frame, 有的 — some of them. The novel has stopped describing the coops and started describing the children, and it does so entirely through ordinary behaviour: playing, crying, eating, nodding off. Not one of them knows anything is wrong.
When Pilgrim had finished looking he resumed his own form and reported back to the Tang Monk: "There are small children in those coops. The oldest are not yet seven and the youngest only five. I do not know why."
罷 is bà, the verb meaning to have done with something, not the light particle that ends a sentence — so 看罷 is "having finished looking." The ages matter and will matter again: the novel is fixing them now so that the number it produces later has faces attached.
Tripitaka, hearing this, fell into perplexity and could settle on nothing.
疑思不定 yí sī bù dìng — turning it over and unable to come to rest. Eight characters, and they close the scene on exactly the same note the reader is on.
Wukong reports what he saw and adds no theory, which is unlike him. He gives the container, the contents, the ages and an admission of ignorance. The chapter has now shown the reader everything except the reason, and it has done it without a single character raising their voice.
The four little clauses about playing and crying and eating fruit are the passage's real work. They could have been left out; the plot does not need them. What they do is make the coops stop being a mystery object and start being full of particular children, one of whom is upset and one of whom is asleep. Everything the chapter does from here depends on that having been established first.