Varicose veins are large, raised, swollen blood vessels that twist and turn. They usually develop in the legs and can be seen through the skin. Spider veins are smaller, red, purple, and blue vessels that also twist and turn. Spider veins are easily visible through the skin, as well.
Common name: Flatworms. 1  Scientific name: many species. Phylum: Platyhelminthes. 2  Description: Although they are called Flatworms, these invertebrates are not flat. They are round-bodied with a flat belly. 3  Fun facts: A Flatworm has a single opening to its stomach, in the middle of its underside.
Body Cavity. Flatworms are acoelomate, which means they do not have a body cavity. Roundworms are psuedocoelomate, which means they have a body cavity between their mesoderm and endoderm layers.he flatworm Planaria and the roundworm Caenorhabditis elegans are both lab organisms that are called worms. However, they are not closely related. Flatworms (phylum Platyhelminthes) and roundworms (phylum Nematoda) are both called worms, but there are many differences between these two types of organisms.