Extremes we find various transitional forms: an active larva, as described above, but with four-segmented, single-clawed legs, as among the rove-beetles and their allies; the body well armoured, but slender and worm-like, with very short legs as in wireworms and mealworms (figs.
Appendages of 1st pair, bi-segmented, completely chelate.
In contrast to these segmented or " merozoic " Cestodes, a few primitive forms have preserved a unisegmental' character and form the Monozoa or Cestodaria.
They resemble those of the sprat and pilchard in having a segmented yolk and there is no oil globule.
The endopodite may be retained as a small segmented palp at the side of the gnathobase or disappear (mandible of Crustacea, Chilopoda and Hexapods).