Object reference not set to an instance of an object. DeMorgan's Recursive Fleas. This is based on the short rhyme by Augustus DeMorgan 1806-1871. DeMorgan was a great mathematician. Unfortunately, he lived in a time when people were too preoccupied with fleas to notice his gift. So he took to writing poetry about fleas, but even then, Mary Shelly criticised him for not writing about fleas that had eyes instead of nipples. In the end, he returned to mathematics a broken and flea ridden man.