On the Development of the Cirripedia. 161 



3. Our Cypris has a length of 1"3 millim. 



4. A description is given of the antennae with the suckers and 

 their glands, the development of which from the glands in the 

 labrum has been mentioned already. The parts of the mouth 

 (small labrum and three pairs of maxillae and maxillipeds) and 

 the natatory feet, as well as the caudal appendages with the anus 

 at their base, are figured and described. The organs of sense, the 

 digestive organs, and the shell-gland, which is now very conspi- 

 cuous, offer scarcely any thing that has not been seen already 

 by Darwin and Claus in the Cyprides of the different species of 

 Lepas. 



IV. The metamorphosis of the Cypris into the youny Lepas. 



1. The pupae are chiefly caught at the very surface of the sea, 

 where they swarm I'ound the dead Velellce, on which they settle. 

 The}' rarely take to a colony of old barnacles. 



2. Soon after settling the new cirri are formed underneath the 

 natatory feet, the head grows out, the eyes are absorbed, and 

 under the Cyj^ris-sheW the primordial valves of the young Lepas 

 appear, which persist during its whole hfe. The Cypris-sheh, 

 with the old natatory feet, is then thrown off. 



3. The young Lepas begins to form the complete shell, and 

 fastens itself more and more by the copious secretions of its glands, 

 which run through the outdrawn and enlarged head into the fixing- 

 antennse. 



4. The cirri of the young Lepas develop a larger number of 

 joints, the shell begins to lose its transparency, the body inside 

 turns over a little, as has been described by Darwin, and the young 

 Lepas is complete. 



ConcltLsion. 



1. As the young stages of the Lepadidse are pelagic, it is 

 only possible to work out their development at sea, and there 

 at certain seasons. We found only once before the large Nauplii 

 of Lepas aiistralis. The development of no one of the Lepadidas 

 has hitherto been known in full; and it seems that even the adult 

 larvae of our commonest barnacles, such as L. anatifera and L. 

 anserifera, are as yet unknown. 



2. The Nauplius stages of Lepas fascicularis have not a dif- 

 ferent morphological value from those of Balanus and other genera ; 

 therefore there is no reason for giving to this stage a particular 

 name. The term " Archizoea " may remain as a remembrance 

 of Dohrn's interesting discovery, but cannot be applied to the larvae 

 of other Lepadidae. 



H.M.S. ' Challenger,' Honolulu, 

 July 28, 1875. 



