River or freshwater crawfish - a very ancient inhabitants of our planet. Their ancestors came from the Jurassic period with long-extinct animals and is believed to paleozoology, crawfish, too, had to disappear from the face of the Earth for many hundreds of thousands of years ago! At this stage, can be considered a miracle of this kind of preservation of biological entities. Cancer belongs to such creatures, which are relatively ignorant of Zoology, man is always in a quandary, not knowing where they are ranked.