Molluscs (Phylum Mollusca) The molluscs, or soft-bodied animals The molluscs are also invertebrate The molluscs having (80,000 species) The molluscs include oysters, mussels, slugs, snails, squids and cuttlefishes. Body form of Molluscs We can divide molluscs into four regions; A dorsal visceral mass which is coiled in the gastropods and in which the internal organs … Read more
Nervous system and sense-organe The most primitive nervous system occurs in the monoplacophorans and amphincurans (e.g. chitons, where it consists of a central nerve ring round the anterior oesophagus with pleurovisceral and pedal cords running back, the former encircling the margin of the mantle, the latter running down the foot, with cross connections between the … Read more
Circulatory system The heart lies within the pericardium which represents part of the much reduced coelom or body cavity. It consists of a single muscular ventricle into which open usually one pair, but in a few cases two pairs, of auricles. Contractions of the ventricle force blood into anterior and posterior aortae; it then circulates … Read more