They belong to the two phyla Platyhelminthes (flat-worms) and Nemathelminthes (thread-worms, &c.).
Now the main divisions are often spoken of as phyla or races.
The animal kingdom has a varying number of divisions, called branches, subkingdoms, or phyla.
It has, however, been held that certain other Cryptogamic phyla had a common origin with the Ferns.
As far back as the record extends they show no sign of becoming merged with other phyla in any synthetic group.
According to it the seven phyla, or tribes, of the animal kingdom are of different value in regard to genealogy.
"division of the plant or animal kingdom," 1868, Modern Latin, coined by French naturalist Georges Léopole Chrétien Frédéric Dagobert, Baron Cuvier (1769-1832) from Greek phylon "race, stock," related to phyle "tribe, clan" (see physic). The immediate source of the English word probably is from German.
phylum phy·lum (fī'ləm)
n. pl. phy·la (-lə)
A taxonomic category that is a primary division of a kingdom and ranks above a class in size.
A group of organisms ranking above a class and below a kingdom. See Table at taxonomy.