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.
The group includes species that are free-living such as planarians but also internal and external parasites such as flukes and tapeworms. The digestive system of most flatworms is relatively simple. It consists of a mouth, pharynx, and either a simple or branched intestine.nimals Invertebrates. Flatworms are divided into the following taxonomic groups: 1  Planarians and relatives (Turbellaria) - There are about 4,500 species of planarians and their relatives alive today. 2  Members of this group are mainly free-living, nonparasitic flatworms.