The larval primary settlement and the changes originated during the metamorphosis of some species of Chilean bivalves, are comparatively studied, being described, the larval and post - larval stages from the veliconcha to late plantigrade. By observing in ropes "anchovetera" nets and plankton samples, in the mitiliculture of Codihué (41º 46'S; 73º 24'W), it was verified for Mytilus chilensis Hupé, 1854 and Aulacomya ater (Molina, 1782), primary settlement on the filamentous algae of genera Enteromorpha with an average size of 33º µ high, minimum average of definitive settlement, byssus positional changes, etc. Information concerning average and number of larval and post - larval attachment to different deep and inmersión period and morphological characters of larval and post - larval of: Bankia martensi Stempell, 1898 (Teredinidae), Pholas chiloensis (Molina, 1782) (Pholadidae) y Chlamys patriae Doello Jurado, 1918 (Pectinidae), are also given.
