Q.Draw neat labelled diagram: Amphioxus

Step 1. Draw an elongated, laterally compressed, fish-like body pointed at both ends, without paired fins, representing Amphioxus (lancelet).

Step 2. Show a rod-like structure running the entire length of the body just below the nerve cord and label it 'Notochord' — present throughout life in this subphylum, unlike in vertebrates.

Step 3. Above the notochord, mark a thin tube as the 'Dorsal hollow nerve cord.'

Step 4. Show a row of segmented muscle blocks along the body and label them 'Myotomes.' …

• Placing the notochord only in an early embryonic stage — in Cephalochordata it persist …