ABSTRACT
This introduction presents an overview of key concepts discussed in the subsequent chapters of this book. The book focuses on the subclass Cirripedia. In sessile cirripedes, the whole of that which is externally visible, May for convenience sake be divided into the / operculum or opercular valves, and the shell, though these parts homologically present no real difference. In nomenclature endeavoured rigorously to follow the rules of the British Association, and have never, at least intentionally, broken through the great law of priority. A discussion on the homologies of the different parts is given under the head of the Metamorphoses of the Balanidae. The prominent mouth consists of a labrum, palpi, mandibles, maxillae, and outer maxillae, the latter resembling a lower lip: these organs may be conveniently spoken of, after Milne Edwards, as gnathites.
