266 A HISTORY OF KECENT CRUSTACEA 



dibles (short), both the latter being biramous and natatory ; 

 (2) a second Naiirplius stage, in which maxillae and maxilli- 

 peds appear as bud-like rudiments ; (3) Metanauplms^ with 

 the carapace commencing, and the mandibular legs lost ; 

 (4) Calyptojjis, with body divided into two regions, and 

 much other development, but eyes not mobile, and no trace 

 of legs or pleopods ; (5) an unnamed intermediate stage, 

 in which the eyes become stalked and mobile ; (6) Fur cilia, 

 with the compound eyes more fully developed, and the 

 anterior legs and pleopods taking form ; (7) Cyrtopia, 

 in which the flagellum of the first antennae becomes 

 elongate and distinctly articulate, so that these appen- 

 dages cease to serve the purposes of locomotion. ' In 

 their metamorphosis,' the authors say, 'the Euphau- 

 siidae stand almost alone, and none of the later larval 

 stages are identical with the Zoeaand other larvae of Deca- 

 pods. They commence their larval life in the Nauplius con- 

 dition, a type of larva frequent in other groups, particularly 

 among the Copepods, Cirripedes, some Decapods, and vari- 

 ous parasitic forms. The larval function of the antenna3 is 

 retained until the commencement of the Cyrtopia stage, 

 a feature which is not usual among the Crustacea. The 

 Calyptopis stage, in which the compound eyes, while 

 undergoing development, are covered by an anterior ex- 

 pansion of the carapace, is a remarkable one, which, so far 

 as we know, is only met with in one other group, an 

 aberrant section of the Decapods, including Lucifer ^ &c., 

 where this condition obtains in the Protozoea stage.' The 

 names of the so-called Calyptopis, Furcilia, and Gyrtopioj 

 stages have been adopted from three supposed genera, 

 established by Dana, who assigned the first two to the 

 Mysidge, and the third to the Euphausiidte, all of them, in 

 fact, representing stages in the development of the latter 

 family. 



Family 4. — Mysidoe. 



The carapace is generally rather small, loosely covering 

 the trunk behind, of which the segments are distinctly 

 defined, though narrow and crowded dorsally. The first 



