Test: Earthworm - 2

The nervous system of the earthworm contains ganglia arranged on the nerve cord. It is present on the ventral side of the body. The nerve ring is present on the dorsal side. It is made of the nerve cord and cerebral ganglia.

The nerve cord of the earthworm bifurcates or divides into two parts at the 3^rd and 4^th segments. It then encircles the pharynx and forms the nerve ring by combining with the cerebral ganglia.

The nerve ring is present on the dorsal side of the body of the earthworm. It is made of the nerve cord which combines with the cerebral ganglia. The nerve ring has both sensory and motor functions.

The sensory system of earthworm lacks eyes. Hence, the earthworm cannot visualize its food. However, it contains receptor cells which helps it to detect vibrations, changes in light intensities and allows it to react to chemical stimuli.

The sense organs of the earthworm are located on the anterior side of the body. Eyes are absent. It contains taste receptors or chemoreceptors. The receptor cells allow the earthworm to detect vibrations and changes in light intensity.

Pheretima or earthworm possesses 4 testes, that is, two pairs. They are present in the 10^th and 11^th segment. The earthworm is hermaphrodite. Hence, it also possesses female reproductive structures.

Vasa deferentia is the common prostate and sperm duct of earthworms. Vasa efferentia is absent. Spermathecae store spermatozoa during copulation. Oviduct is a part of the female reproductive system.

The spermathecae stores spermatozoa during mating. Four pairs of spermathecae are present in earthworms. They occur in segments 6 to 9. It is not an accessory organ. It is not a vestigial organ.

The earthworm possesses one pair, that is, two ovaries. They are attached at the septum between the 12^th and 13^th segments. Egg cells or ova are formed which subsequently get fertilized to zygotes during fertilization.

In the body of earthworms, the ovarian funnels are present below the ovaries. The ovarian funnels open up into the oviduct and join together. They lead to an opening on the ventral side known as the female genital pore.