Ningyo is the Japanese "mermaid". In ancient times it was described as half fish and half monkey, but with a human face. It has a beautiful voice but causes storms and brings misfortune. If you eat the ningyo you will become immortal. (Strangely enough I believe Ningyo is also a Japanese word for doll.) I think maybe this whole half monkey, half fish myth resulted in people making the fiji (feejee) mermaids.
What's a fiji mermaid? Prepare yourselves for some wild wacky icky stuff!
Back in the 1800s everyone loved carnivals and freak show and strange oddities. Remember this was before TV, telephones and not everyone had a camera just laying around. So traveling carnivals were the best way to see all the interesting thing that we see today on Ripley's Believe it or Not. P.T. Barnum was the king of wowing an audience so when he had an opportunity to get a mermaid for his show he jumped on it.
Long before this, in Japan, several shrines had "found" mermaids. Most likely the preists created these monkey/fish in order to awe the locals. A few of these old, mummified mermaids can still be found in the care of temples and shrines around Japan.
This picture is one of the "mermaids" that is still in a shrine in Japan.
The Fiji mermaid came into Barnum's possession via his Boston counterpart Moses Kimball, who brought it to Barnum in late spring of 1842. On June 18, Barnum and Kimball entered into a written agreement to exploit this "curiosity supposed to be a mermaid." Kimball would remain the creature's sole owner and Barnum would lease it for $12.50 a week. Barnum christened his artifact "The Feejee Mermaid" and began to work the press. There were ads in papers, everyone was talking about this "mermaid" and no one had even seen it yet (the ad on the left is one of these 'plants' I believe.) Many many people fell for the hoax and believed that a torso and head of a baby monkey sewn to the back half of a fish and covered in paper-mâché was the real thing. The original exhibit was shown around the United States, but was lost in the 1860s when Barnum's museum caught fire.
Despite the loss of the original mermaid there are still many "floating" around. You can see the older ones at shrines in Japan, and I've even seen one in Myrtle Beach at the Ripley's museum.
So that's what I know about the Ningyo. TakaSachi, one of my Swimmers, is Japanese and I'd love any corrections or additions that might be offered.