In addition, this species also lacks a notochord. So, it should be clear why these species are called Hemichordates, and are not included with the true chordates. This group undergoes complete metamorphosis from a mobile larva to a sessile adult, resorbing the tail and notochord. Some are solitary, most are colonial. Appendicularians do not metamorphose, and are able to reproduce as free-swimming larvae.
Tunicates differ strongly in appearance between the adult and larva.
The larval stage lasts only a few days, and ends when the larva attaches to a substrate and metamorphoses into an adult. This example should illustrate to you that although chordates are said to have four basic things in common, these characteristics need not be retained throughout life for an animal to be considered a chordate. Rather, they must only be present in an individual at some time during development. 2.22 - 2.24 in text. Amphioxus are 2-3 inches in length, and live on seashores throughout the temperate zone.