CRUSTACEA. 



bi ramous, and an unscgmcnted body. The second pair of antenna: has not 

 however the colossal dimensions so common in the lower types. A mouth is 

 present, but the anus is undeveloped. 



After the first moult three pairs of prominences the rudiments of the 

 two maxilla: and ist maxillipcds arise behind the Nauplius appendages 

 (fig. 212). At the same time an anus appears between the two limbs of 

 a rudimentary caudal fork ; and an unpaired eye and upper lip appear in 

 front. After another moult (fig. 212) a lower lip is formed (UL) as a 

 pair of prominences very similar to true appendages ; and a delicate 

 cephalo-thoracic shield also becomes developed. Still later the cutting blade 

 of the mandible is formed, and the palp (Nauplius appendage) is greatly 



FIG. tit. NAUPLIUS OK EUPHAUSIA. (From Claus ; after Metschnikoff.) 

 The Nauplius is represented shortly before an ecdysis, and in addition to the 



proper appendages rudiments of the three following pairs are present. 



OL. upper lip ; UL. lower lip ; Md. mandible ; Mif. and Ar". two pain of 



maxillae; mf. maxilliped i. 



reduced. The cephalo-thoracic shield grows over the front part of the 

 embryo, and becomes characteristically toothed at its edge. There are also 



302 



