Answer:
Flatworms
Step-by-step explanation:
- Cephalization is the process of development of the end of the animal where the head is formed.
- The early organisms did not have any well defined anterior end but the Higher animals started showing cephalization which allowed them to move in a particular direction and the nerve cells started gathering in front.
This was accompanied by bilateral symmetry and since the flatworms are bilaterally symmetrical, they were the first ones to show cephalization.