Read it through once

Nature cakes a fish's eyes over with parasites, so that it shan't be able to avoid its enemies or find its food. She sends parasites into a star-fish's system, which clog up its prongs and swell them and make them so uncomfortable that the poor creature delivers itself from the prong to ease its misery; and presently it has to part with another prong for the sake of comfort, and finally with a third. If it re-grows the prongs, the parasite returns and the same thing is repeated. And finally, when the ability to reproduce prongs is lost through age, that poor old star-fish can't get around any more, and so it dies of starvation.