An animal derived from only two germ layers are called diploblastic animals. Eg: Poriferans, Coelenterates.
diploblast
Triploblastic. Google said so. Also, I cut one open and checked.
No, diploblasts do not have a mesoderm. They are simple animals with two embryonic germ layers (ectoderm and endoderm) that give rise to the different tissues and organs in their body. Mesoderm is a germ layer found in triploblastic animals.
Earthworms are Coelomates. They posses a true coelom, which is a body cavity that is completely lined by tissue derived from the mesoderm. This body cavity can either be empty air-filled space separating the digestive tract from the outer body wall, or fluid-filled space. Since triploblastic animals are defined as animals having three germ layers, earthworms is considered a triploblastic animal for it possess a endoderm, a mesoderm, and a ectoderm.