388 



COMPARATIVE ANATOMY 



CHAP 



a Nauplius and a Cypris stage in the course of their developments. These larvae differ 

 from the corresponding larvae of Sacculina not only in the possession of an enteric 

 canal, but in a few other points as well. The Nauplius larva of the Cirripedia is 

 characterised by a dorsal shield with frontal horns and posterior pointed processes, and 

 by a large upper lip. Frequent moults lead to the Cypris-like larva (Fig. 260) ; this 

 has a bivalve shell with shell muscles ; its anterior antennae have become adhering 



ab 



Tf 



FIG. 260. Cypris-like larva of Lepas fasciculata (after Glaus). 



antennae. The posterior antennae and mandibular feet of the Nauplius larva have 

 disappeared, and so has the upper lip. By the side of the median eye a paired com- 

 pound eye has arisen. Behind the mandibular feet of the Nauplius simple anterior 

 and perhaps also posterior maxillae have begun to form. The trunk consists of 6 

 segments with 6 pairs of biramose feet serving for swimming. The abdomen has 

 2 furcal appendages. A cement gland opens on the 2d joint of the adhering antenna, 

 which is provided with a sucking disc. 



ca 



rf 



FIG. 261. Pupa of Lepas pectinata, in optical section (after Glaus). In Figs. 260 and 261, the 

 same letters are used : pa, paired eye ; ua, unpaired Nauplius eye ; rf, trunk feet, in Fig. 261 with 

 the tendril-like feet beginning to form inside ; 1, anterior (adhering) antennae ; L, liver ; sm, occlusor 

 muscle of the scuta ; ab, abdomen ; ca, carina ; t, tergum ; sc, scutum ; cd, cement gland. 



The Cypris-like larva attaches itself by means of its adhering antennas. A pupa 

 stage follows (Fig. 261), during which the organs of the adult Cirripede form under 

 the larval skin. Within the maxillae and the 6 pairs of trunk feet of the Cypris-like 

 larva the mouth parts and the 6 pairs of tendril-like feet of the adult Cirripede begin 

 to form. In the Lepadidce the head grows out anteriorly into the stalk which 

 carries the minute adhering antennae, and under the Cypris shell the 5 shell pieces 



