Barreleye. Sometimes called a "spook fish," the barreleye has a completely transparent head.
Betta's were bred and kept for competition fighting in Thailand by the people of Siam in the 1800s. The King of Siam saw how captivated people were by these fighting fish and decided he should start licensing and collecting them. In 1940, the King gave some of these award winning to Dr. Theodor Cantor who called them Macropodus Pugnax. Mr. Tate Regan realized that there was already a species called Macropodus Pugnax in 1909 and renamed the fighting fish Betta Splendens.