Sentence:  The taxonomic distribution of <WSD>nauplii</WSD> within Crustacea raises questions, however, about the evolution of a nonfeeding but swimming <WSD>nauplius</WSD> from an embryonized <WSD>nauplius</WSD>. Most malacostracans lack a free <WSD>nauplius</WSD> stage. Euphausiaceans and dendrobranchiate shrimp, which hatch as nonfeeding <WSD>nauplii</WSD>, are the exceptions. Inferred phylogenies of malacostracans imply that either the ancestor lacked a free <WSD>nauplius</WSD> and free <WSD>nauplii</WSD> subsequently evolved again, or that egg <WSD>nauplii</WSD> evolved multiple timesnb.... 
Meaning of the word marked with <WSD> tags:  A crustacean larva that has three pairs of locomotive organs (corresponding to antennules, antennae, and mandibles), a median eye, and little or no segmentation of the body. (from mid 19th c.)