Q.In Ascaris, __________.

Aschelminthes (Greek askes, cavity; helminths, worms), previously called Nematoda, are the round worms, named for their circular cross-section. They are triploblastic, bilaterally symmetrical, pseudocoelomate animals with organ-system organisation, free-living or parasitic on plants and animals.

The unsegmented body is covered by a tough, transparent, protective collagenous cuticle. Aschelminthes have a complete alimentary canal with a well-developed mouth, muscular pharynx, and separate anus — the first phylum on the tree to achieve this, unlike the incomplete gut of Platyhelminthes.

Unlike the hermaphrodite flatworms, sexes are separate in Aschelminthes, with pronounced sexual dimorphism (females typically longer than males). Fertilisation is internal; most species are oviparous (e.g. Ascaris), a few ovoviviparous (e.g. Wuchereria). Development may be direct or indirect. Examples: Ascaris lumbricoides, Enterobius vermicularis (pin worm), Wuchereria bancrofti (filarial worm), Ancylostoma duodenale (hook worm).