Question

Mention the animals exhibited a ‘tube-within-a-tube organization.​

Answer 1

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Cnidarians and some flat warms are the first animals to exhibit a 'tube-within-a-tube' organisation. Body cavity is pseudo- coelom..

Answer 2

Explanation:

The animals such as Nematodes and Rotifers exhibited a 'tube-within-a-tube' organization for the first time.