Let us now consider some other creatures that resemble vertebrates in some ways, and help to form the group of Chordata.
Perforating gills (of vertebrates and other Chordata), 142, 144.
This is the case with the larv of the Myriapoda, the Crustacean larv, and with the larval forms of the Chordata.
All the vertebrates are included in a single phylum—Chordata.
The higher animals begin with the twelfth phylum, namely, the Chordata, or vertebrates.
The epiblast in a large number of Chordata arises as a single row of more or less columnar cells.
Is such an element to be recognized in the head of the Chordata?
This feature in the development is a nearly certain indication that the Chordata are a very primitive stock.
It may be convenient to shew in a definite way the bearing of the above speculations on the phylogeny of the Chordata.
The most characteristic organ of the Chordata is without doubt the notochord.
Chordata Chor·da·ta (kôr-dā'tə)
The phylum of animals whose members have a single dorsal nerve cord and a notochord and gill slits during some stage in their development.