Answer: Not a human parasite; most closely resembles bean sprouts.
Although many of you suggested that these might be Ascaris adult worms, the blunt ends and irregular indentations are not consistent with this identification. Real Ascaris would have a smooth cuticle and a tapered head and tail.
Because there are many parasite mimics that are routinely submitted to the laboratory, we always carefully examine submitted material using a dissecting microscope. If we get something that might be a worm, we confirm our identification by trying to manipulate the object and express eggs from them. Mucus strands may resemble worms, but easily fall apart with manipulation. Bean sprouts, on the other hand, would retain their firmness, but would easily be broken apart using gentle pressure with forceps. Also, no eggs would be seen in fluid expressed from them.