THE C IRRIPEDIA . 
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 tarns 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 Anelasma lives 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. 
