Note 1 — Part 1.-- Vertebrata. (continued 2)

Having the notochord reaching in front of the brain. Cephalochorda = Amphioxus. 2. Having the notochord reaching anteriorly to the mid-brain, a brain of three primary vesicles and a skull. Craniata = all "true vertebrata": fishes, amphibia, reptiles, birds, and mammals (Vertebrata of Balfour). 3. Having the notochord confined to the tail. Urochorda = the ascidians, or sea-squirts, certain forms of life only recently recognised as relatives of the vertebrata.