r/o 



NATURAL HISTORY. 



are in perpetual movement, being alternately thrown out and retracted with great rapidity ; and that, 

 when fully expanded, the plumose and flexible stems form an exquisitely beautiful apparatus,, 

 admirably adapted to entangle any nutritious atoms or minute living creatures that may happen 

 to be present in the circumscribed space over which this singular casting-net is thrown, and drag them 

 down into the vicinity of the mouth, where, being seized by the jaws, they are crushed and prepared 

 for digestion. No sense but that of touch is required for the success of this singular mode of fishing ; 

 and the delicacy with which the tentacles perceive the slightest contact of a foreign body shows that 

 they are eminently sensible to tactile impressions." 



The process of exuviation common to the class Crustacea cannot take place with the shell in the 

 CIRRIPEDIA, but the delicate skin of the articulated cirri (whence their name " Curl-footed"), the 

 tunic lining the sac, and the integuments of the whole body are regularly moulted. All 

 the Cirripedia grow rapidly; and Darwin says, "in accordance with this rapid growth is the 



frequency of periods of exuviation. 

 Mr. Thompson kept twenty specimens 

 of Balanus balanoides alive, and on the 

 twelfth day he found the twenty-first 

 cast-off integument, showing that all 

 had moulted once, and one individual 

 twice within the period. This fre- 

 quency of exuviation explains the 

 astonishing masses of exuvia which 

 Mr. Peach assures me he annually has 

 observed off the coast of Cornwall ; 

 they are most abundant in April and 

 May, but he has seen quantities also 

 in September. He could easily, he tells 

 me, have filled several quart-measures 

 with them." 



The only difference of the growth 

 of the shell in the Cirripeds and that of other Crustaceans is the new layers of thin shell which 

 grow up or are deposited over the internal surface of the valves, the old shell adhering to the outside 

 of the new one ; the margins are added to slowly, but not continuously, instead of being formed 

 at a single period. 



"In the genus Alcippe, the whole of the external membranes are moulted, excepting the surface 

 of attachment ; but these Cirripeds live in cavities, which they form for themselves, and are thus 

 protected." 



" The most remarkable fact concerning the peduncle of Lithotrya is that the outer tunic, 

 together with the calcareous scales with which it is covered, is moulted at each successive period 

 of exuviation and growth. I demonstrated this fact in L. dorsalis and L. tmncata, by removing the 

 old tunic, and finding a new membrane with perfect calcified scales beneath ; and as these two species 

 are at the opposite extremes of the genus, no doubt this fact is common to the whole genus. I know 

 of no other instance amongst Cirripedia in which calcified valves or scales are moulted. I am not 

 certain that the whole skin of the peduncle is thrown off in a single piece, though it is almost certain 

 in the case of the uppermost and lowest portions." 



In viewing Lepas in comparison with other forms, it is necessary to treat it as attached by 

 its head, its thoracic appendages serving as cirri, its abdominal segments being suppressed or 

 undeveloped. 



The Cirripedia extend over the whole world, and all the species are marine ; some are parasitic 

 on Whales, others on the Turtle, and many forms live floating about on ships and timber. 



Fig. 41. LARVAL FORMS OF CIRRIPEBIA. 

 A, Nauplius of Balanus ; B, Larva of Chthamalus stellatus; c, Larva of Lepas australis. 



HENRY WOODWARD. 



