Larvae of the stone crab,Menippe mercenaria Say, were reared from egg to a true crab stage in 27 days on a diet ofArtemia nauplii. They were successfully cultured in swarms and placed in small compartments where their individual development was studied. Six zoeal stages were found and described, although only five are believed to occur normally in nature. One molt per zoeal stage was noted, and from 3 to 6 days were spent in each stage. Pre-zoeae were observed but these did not molt into a first stage. Such diagnostic characters as size and shape of antennae, and segment and seta numbers of endopodites, maxillules, maxillae and second maxillipeds, were constant in all zoeal stages. Telson appearance and chromatophore occurrence may also be helpful in identification. Comparisons were also made between known xanthid zoeae andMenippe zoeae. Experiments on salinity and temperature tolerance of the zoeae indicate that in a temperature range of 23 to 25°C, zoeae may not be able to survive in salinities of 27‰ or lower.