470 DECAPODA. 



for swimming, and the third of them (mandibles) is without a 

 trace of the future blade. The body has no carapace, and bears 

 anteriorly a single median simple eye. Posteriorly it is produced 

 into two bristles. 



After the first moult the larva has a rudiment of a forked 

 tail, while a dorsal fold of skin indicates the commencement of 



FIG. 214. NAUPLIUS STAGE OF PEN^EUS. (After Fritz Mullen) 



the cephalo-thoracic shield. A large provisional helmet-shaped 

 upper lip like that in Phyllopods has also appeared. Behind 

 the appendages already formed there are stump-like rudiments 

 of the four succeeding pairs (two pairs of maxillae and two pairs 

 of maxillipeds) ; and in a slightly older larva the formation of 

 the mandibular blade has commenced, together with the atrophy 

 of the palp or Nauplius appendage. 



Between this and the next observed stage there is possibly a 

 slight lacuna. The next stage (fig. 215) at any rate represents 

 the commencement of the Zoaea series. The cephalo-thoracic 

 shield has greatly grown, and eventually acquires the usual 

 dorsal spine. The posterior region of the body is prolonged 

 into a tail, which is quite as long as the whole of the remainder 

 of the body. The four appendages which were quite functionless 

 at the last stage have now sprouted into full activity. The 



