The poem is a metaphor poem written in quatrains. A quatrain is a four line stanza. These stanzas are all four lines. They each have the ABBA rhyme scheme, meaning the first and fourth lines rhyme and the middle two lines rhyme.
Beautifully Janet slept
Till it was deeply morning. She woke then
And thought about her dainty-feathered hen,
To see how it had kept. (poetryoutloud.org)
The use of this format serves to accentuate the youthful, sing-song nature of the poem.
The poem is a metaphor, because it compares Janet waking up with Janet coming to an understanding about death. The metaphor of Janet waking is Janet growing up, and learning an important lesson of life. Things die. Nothing remains the same forever. At the beginning of the poem, Janet lives in a bubble of safety and security. By the end, she realizes that there is sadness in life. The last stanza demonstrates this.
And weeping fast as she had breath
Janet implored us, “Wake her from her sleep!”
And would not be instructed in how deep
Was the forgetful kingdom of death.
Janet has to learn that once something dies, it dies. This is something that all children learn, eventually, but it is never an easy lesson. Sometimes growing up is hard.