The Morphology of Balanus improvisus Darwin and Balanus amphitrite niveus Darwin During Initial Attachment and Metamorphosis

Among the Cirripedia are free-living and parasitic forms without the slightest resemblance to each other as adults, having only the six nauplius and single cypris stages in common. The close similarity of the larval stages is in marked contrast to the wide divergence of form and mode of life of the adults. Because of this similarity, a study of the larvae of any cirripede is a useful aid to comprehension of the entire group. With regard to fouling of ships' bottoms, the most important phase of development is the metamorphosis from cypris to adult, for at this point in their life history barnacles abandon the free-swimming planktonic life to become sessile. Because of the dearth of detailed information about stages immediately following attachment, the present study was initiated.