Question

Why is the skeleton of earthworms and snails called a liquid skeleton ??

Answer 1

because they consist mucilagenous layer which secrets mucilage..

Answer 2

Actually snails and earthworms are devoid of what we call a bony skeleton. Their body only consists of certain fluid at high pressure that keeps their body near to rigid. This liquid skeleton protects their body from collapsing. The size of snails and watermark are considerably small.