THE HOLLOW DORSAL NERVE CORD:
-used for support in the early stages of a Chordates life
-runs down the length of the organism
-connects to an organism muscles

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Notochord

The Notochord is also used for support in the embryological stages of a Chordates life.

Pharyngeal gill slits

Pharyngeal gill slits are used for filter feeding in Chordates. 

Tail

The tail is only present in embryological stages and stretches the length of the Chordate.