Jonathan Mayhew, one of my very fit though sweltering though very few readers, came all the way back from Spain to work on the Rest Note puzzler. & he's almost there. Anybody else want to catch this train? You have to name the poet, the poem, & the particular line.
Big clue : remember, this is a poem which began on April 26th, the day Teddy Roosevelt emerged alive from the Amazon jungle, & also the day Hart Crane disappeared into the Caribbean. And Teddy, in his memoirs, credits his lifelong interest in natural history to seeing a certain baby aquatic animal on the NYC fish market docks.