How does the line “Black snake! Black snake!” contribute to the structure of the poem "The Black Snake"?

Monsters of the deep the ocean is full of mysteries and amazing creatures. since the first sailors left their home shores and set off for adventure, stories have been told of the strange and wondrous beasts encountered on the open ocean. with only glimpses and imagination-enhanced stories to go on, humans have made many an interesting creature into a monster. the truth is, the ocean's scariest creatures inhabit such extreme depths that humans are rarely, if ever, threatened by them. that does not mean they are not the stuff of nightmares. consider, if you will, the following frightful fiends. atlantic hagfish part eel, part sea snake, this sea serpent may have inspired many stories. lacking the scales that most fish have, the hagfish secretes the most amazing slime to protect itself. this slime may be used to suffocate predators. the slime includes small fibers that make it almost impossible to remove. but the hagfish's truly horrific nature lies in what it does to its prey, not its predators. with an excellent sense of smell that compensates for almost total blindness, the hagfish will locate and latch on to a victim. with a circle of razor sharp teeth, the hagfish bores a hole into the side of its now-doomed prey. once the hole is complete, the hagfish just welcomes itself inside for a meal of fish innards. it essentially eats its prey from the inside out. like other deep-sea monsters, however, hagfish are seldom a nuisance to humans. they live most of their lives at depths of up to 5,600 feet. in fact, they prefer a soft sea bottom so they can quickly bury themselves to hide from threats. gulper eel another, more hideous, fiend of the deep is the gulper eel. this creepy critter is part eel and part giant pouch. like a pelican's enormous pouch-shaped mouth, the mouth of the gulper eel can open quite wide to gulp prey. it has a long tail tipped with a glowing organ that is used to lure in prey. in part to its tail, the gulper can reach up to six feet in length. because its tail is so thin, it is not able to pursue prey with any speed, but it can scoop up hundreds of small crustaceans or shrimp in one bite. often swimming through these prey groups with its mouth wide open, its large jaws allow it to feed on squid and other creatures much larger than itself. gulper eels have only been studied because they sometimes get caught in the nets of fishermen. the depths they inhabit make it quite difficult for scientists to study them. they can go as deep as 6,000 feet, well beyond the abilities of humans to pursue them. vampire squid perhaps the most frightening of the deep-sea monsters is also the smallest. the vampire squid reaches lengths of only six inches. it is also one of the most ancient of the deep-sea monsters. scientists believe it to be the last surviving member of its order. to see the vampire squid is to wonder how many kinds of sea creatures have been mashed into this one odd-looking spook. part squid, part octopus, and part fish, the vampire squid has features of all of these. first, it has large fins at the top of its head that look like ears. flapping like dumbo, the squid uses these fins to get around. it also has tentacles and a large bulbous head like an octopus. its arms, however, are connected by webbing that allows it to form a cloak around itself when frightened. like the octopus, it can change its colors, even making its cloak so dark that it appears invisible. remarkably, it has the largest eyes compared to its body size of any creature on earth. despite its mere six-inch length, its eyes are as big as those of a large dog. with its glowing orbs of eyes and its disappearing tricks, it's no wonder it's named after one of the most feared creatures of legends and folklore: the vampire. these creatures make one wonder not just about the odd members of the deep-sea community, but also what mysterious things inhabit the regions never visited by humans. what may be lurking in the deepest, darkest corners of the deep blue seas? one thing we know for certain, much like the outrageous monsters we conjure in our worst nightmares, the deep ocean is an equally imaginative source of shock, awe, and outright fright. what are the key differences between the atlantic hagfish and the gulper eel? use details and quotations from the text to support your answer.