THE CIRRIFEDIA. 479 



terminal joints of the antennae invariably remain cemented to the 

 surface of attachment. The carapace separates all round the 

 orifice, but the delicate tunic lining the sac and investing the body 

 and legs of the pupa is not shed for a considerable time after- 

 wards. At this period the Cirripede is more or less horizontally 

 disposed with regard to the surface upon which it adheres, but 

 immediately after the moult a most important change of position 

 occurs. The Cirripede turtts up and remains at right angles to its 

 attachment, so that the tail end is upwards, and the cirri — the 

 legs — being upwards also. A moult of the membranes just noticed 

 occurs, and the traces of the valves of the complicated shell are 

 seen forming. The valves or pieces of the permanent shell are at 

 first membranous, but calcareous structures soon become formed 

 under them. 



Small parasitic and very strange-looking creatures were noticed 

 by Mr. Darwin upon and within the shells of mature Cirripedes, and 

 after much patient research he discovered that they were the males 

 of the shelly females or bi-sexual barnacles. Many kinds of these 

 males are without mouth or thorax, and have very defective cirri. 

 Some have rudiments of valves, and all lead a life at the expense 

 of the protecting female. It is probable that the larvae of these 

 imperfect creatures are of the same shape as those of the fully 

 developed females, but the retrograde metamorphosis has been 

 greater in their case than in that of the latter. 



Some of the pedunculated Cirripedes, which are parasitic upon 

 large marine animals, have their structures modified and altered 

 from the original form to meet the emergencies of their condition. 

 Thus, an AnelasmaXwo.'s, upon the outsides of sharks in the northern 

 seas, and its peduncle is immersed in their skins ; and Mr. Darwin 

 could find no cement glands or cement. The surface of the 

 peduncle is beset with much-ramified hollow filaments, which 

 penetrate the shark's flesh like roots. Now the cirri and mouth 

 organs of these Cirripedes are very defective in their structure, and 

 the presence of the hollow filaments of the antennae explains why, 

 for they suck up the juices of the shark, and replace the functions 

 of the food-catching and digesting apparatus. Mr. Darwin found 

 the stomach empty in the specimen examined by him, and the 

 palpi and external maxillae were nearly absent. 



