ABSTRACT
The nervous system of the Cestode Bothriocephalus achelognathi, which belongs to the order Pseudophyllidea was studied, as one of the most economic fishes in Iraq [Barbus esocinus] [Heckel, 1843] for the period Spring - Summer at year 1994 from lake Sad Sadam in Mosul, north of Iraq. The nervous sytem was studied using Acetylthiocholine Iodide for the detection of acetylcholine esterases [Achl]. The nervous system consists of two cerebral ganglia which are connected by a cerebal transverse commissure, located at the sides of the bothria. From these two ganglia two nerves arise anteriorly, and eight nerve trunks posteriorly. These trunks are connected together by eleven transverse commissures. Along the media venteral trunk, there are eleven post - lateral ganglia in each segment. A comparsion was made between the nervous system of this specie of cestode and those of other related species which belong to the same order. Positive enzymatic reactions were observed in non- nervous organs such as gonad anlagen and other genital organs