ONTOGENY OF THE SINUS GLAND AND OF THE ORGAN OF BELLONCI IN LARVAE AND POSTLARVAE OF THE EUROPEAN LOBSTER HOMARUS-GAMMARUS

The topography of larval (stages I, II, III) and postlarval (stage IV) eyestalk of Homarus gammarus was studied by light and electron micros copy. The general structure (ommatidian layer and the three nervous ma sses) at hatching is similar to the adult eyestalks' organization. The sinus gland is present and contains neurosecretory granules as easly as stage I. Its size and the density of granules increase through deve lopment. The presence of neurosecretory granules and exocytosis vesicl es in the sinus gland of stage I larvae demonstrates that the sinus gl and is functional at the beginning of the larval development. The orga n of Bellonci is also present at the first larval stage; it is located at the opposite side of the sinus gland and presents two aspects: a v esicular form and the classical onion bodies.