Metamerism Can Be Divided Into Two Main Categories:
In obvious metamerism, there is a sequential reiteration of homologous organs, as nephridia, nerves, muscles, regenerative organs, limbs and so on in each portion however these organs work in a joint effort with the others.
Advancement of Metamerism.
Development of Pseudometamerism.
Hymen (1951) suggested that pseudometamerism advanced in turbellarians and nemertians first by sequential reiteration of organs, especially the regenerative organs for expanding fruitfulness. Afterward, these organs were isolated by cross-dividing of body delivering metamerism.
Turbellarians are not divided yet some have sequentially rehashed organs.Nemertians are moderate among turbellarians and annelids and have a specific coelom called rhynchocoel in which organs are sequentially rehashed however not isolated by septa. Precursors of metameric creatures were maybe like nemertians and archiannelids, for example, Polygordius, which are additionally not obviously divided creatures.
Advancement of True Metamerism.
Metamerism in Chordates.