ABSTRACT
Histological and histochemical techniques were used to study the structure of the ink apparatus and the funnel organ of the squid Sepioteuthis sepioidea (Blainville, 1823). The ink apparatus is composed of ink sac, ink gland and ink duct. The wall of the ink sac consists of four layers: outer connective tissue capsule, muscularis, sub-mucosa and mucosa. The Ink gland lies at the base of the ink sac and consists of basal (caudal) and apical regions. The ink gland is composed of numerous interconnected, sponge like lamellae traversed the cavity of the gland. These lamellae are consisted of connective tissue covered with one layer of glandular epithelium. The duct of the ink sac consists of an outer connective tissue layer, muscular layer and lined with a single layer of epithelial cells. In general the ink produced by cephalopods is secreted from two glands: ink gland which produces a black ink containing melanin and the funnel organ (a mucus-producing gland) which located on the internal surface of the funnel. The funnel organ consists of two lateral pads and a median pad that has the same histological structure. The lateral pad consists of epithelial and sub-epithelial layer. The epithelial layer is composed of a single layer of columnar cells, while the sub-epithelial layer contains many secretory cells.