Study island ? Help plz

What is the “narrow cell” in line 15 of “elegy written in a country churchyard”

Seven pleiades entranced in heaven, form in the deep another seven: endymion nodding from above sees in the sea a second love. how do the ideas in the excerpt compare to poe’s ideas in "the poetic principle"? this celebration of love offers the “lessons of truth” that poe encourages. this scientific reference relates to the “precepts of duty” that poe praises. this reflection of the night sky offers a “contemplation of the beautiful” that poe encourages. this image of heaven encourages the “incitements of passion” that poe praises.

What is the phrase a tiny shoot of phase prikled by the mind