Question

The rhynchocoel is a ________.

a. circulatory system

b. fluid-filled cavity

c. primitive excretory system

d. proboscis

Short answer

Option B is the correct answer.

Step-by-step solution

Introduction

The rhynchocoel, a tubular cavity that houses a nemertean worm's introverted proboscis, is sometimes compared to the coelom.

The explanation for the correct answer.

In these animals, the rhynchocoel is a hollow filled with fluid that extends from the head to almost two-thirds of the length of the gut. The retractor muscle, which is connected to the rhynchocoel wall, has the ability to expand or retract the proboscis.

The explanation for the incorrect options.

As a result, the term "rhynchocoel" refers to a cavity rather than the primordial excretory system, proboscis, or circulatory system.