Q.What is metamerism?

[!TLDR] Metamerism is the division of the body into a linear series of repeating segments. …

[!ANSWER] Metamerism is the segmentation of an animal's body into a repeating series of similar units along its length.

In a metameric animal such as an earthworm, the body is divided into a linear series of segments (metameres), and each segment typically repeats much of the same internal organisation — its own set of muscles, its own pair of nerve ganglia connected to the main nerve cord, and, in Pheretima, its own set of excretory organs (nephridia) — even though a single gut and nerve cord run continuously through all the segments. This segmental repetition allows the muscles of each segment to contract semi-independently, giving the animal finer control over local body movements (important for burrowing locomotion), and also provides a degree of redundancy, since damage to one segment need not disable the whole animal's functioning. …

• Confusing metamerism (true internal segmentation, with repeated organs) with merely external, superficial ring-like markings. …