The document describes several larval forms of crustaceans: - The nauplius is the fundamental larval form, with an oval unsegmented body and three pairs of appendages. It undergoes molting and transforms into the metanauplius stage. - The metanauplius has an elongated body with frontal organs and rudimentary appendages. It molts into the protozoea stage. - The protozoea has a differentiated cephalo-thorax and abdomen, covered by a carapace. This develops into the zoea stage, which is the second important larval form with a developed cephalo-thorax and six-segmented