ORDER I. The INTESTINA, are the most simple animals, being perfectly naked, and without limbs of any kind.—This order contains 21 genera, viz. Ascaris, Trichocephalus, Uncinaria, Tilaria, Scolex, Ligula, Linguatula, Strongylus, Echinorhynchus, Haeruca, Cucullanus, Caryophyllens, Fasciola, Taenia, Furia, Myxine, Gordius, Hirudo, Lumbricus, Sipunculus, Planaria.