WAEC - Biology (2017 - No. 1)
Which of the following groups of animals do not possess a nervous system?
Porifera
Cnidaria
Platyheminthes
Nematoda
Explication
Porifera are 'pore bearing' organisms, commonly known as sponges, are the only multicellular organisms without a nervous system. Their response to stimuli is by a contraction in their bodies.