In the turbellaria we find for the first time a true body-wall distinct from underlying organs.
"The Whence and the Whither of Man" by John Mason Tyler
They developed out of the turbellaria of the sixth stage by forming a true body cavity (a coelom) and blood in their interior.
"Was Man Created?" by Henry A. Mott
Those that are usually dwelt on are treated with the Rotifers and Nematoda and Turbellaria.
"Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 5" by Various
They developed out of the Turbellaria of the sixth stage by forming a true body-cavity (a coelom) and blood in their interior.
"The History of Creation, Vol. II (of 2)" by Ernst Haeckel