THE ANIMAL LIFE OP TIIH (JROI'I'. 473 



it will iniinediately seek shelter in the iieai'est shell at ha ml. TIh' cral) will 

 back into its new^ home, inserting its tender abdomen into the shell until the 

 aperture is phisged l)\- its elaws and the hard part of its body. 



Often at low tide during the day a dozen or more of tlu'se active creatures 

 will be found carefully hidden away under some loose stone on the reef. 

 When disturbed they start oft' in all directions, each shellcrcd in a ditferent 

 species of shell and each carrying its own lioi-i'owcd house on its hack like a 

 snail. Not infrequcMitly other animals, as ])aruacles, oysters and sea-anenionies 

 take up tlieir permanent residence on the shell occupied by a hei-mit crab and 

 are in this Avay cai'ried about l)y them. 



Barnacles. 



There is little in the apj)earance of adult Ijarnadcs to suggest that they 

 are in any way related to their crab antl lobster cousins. Such is the ease, 

 nevertheless, and by zoologists they are looked upon as furnishing an excellent 

 example of degeneration through quiescence, for wdien they hatch fi-om the 

 egg they are fi-ee swimming animals that closely I'esemble the young ^•' form 

 of the crabs and shrimps, with btit a single eye. Later on they have six pairs 

 of swimming feet, a pair of compound eyes, and two well-developed antenna'. 

 and are still free swimming animals. But when the ci-eatute makes the linal 

 change to the adult condition, it attaches itself by means of a cement-like sub- 

 stance to a stone, shell, pile or tioating log, or to the bottom of a ship, and 

 gives up all attempts at locomotion. Tt then loses its compound eyes and its 

 feelers, and develops a protecting shell. The swimming feet become modified 

 into grasping organs and henceforth it abandons any attempt to look and act 

 like other Crustacea and devotes its energies to fanning such food as comes its 

 way into its mouth, with its legs. There are two main i:roui>s of tlu' ordei-.'^ 

 including the barnacles, that are lia])le to attract attention on the seashore. 

 One family '"' includes the stalked species familiarly known as goose mussels or 

 goose barnacles, a name derived from an ancient belief that if one fell from its 

 support it turned into a goose. They usually occni' hanuini^ by the long stalk ''• 

 to the bottoms of ships, to floating tindier or submerged wood of any kind. 

 The sessile barnacles,^" acorn shells, or ])ioeoe as they are called by the natives, 

 are everywhere abundant along the shoi'(\ The entire animal is enclosed in n 

 tent-shaped shell composed originally of six pieces, which is capped hy an 

 operculum made up of four valves. 



Unfortunately, the shore forms ha\e ]H)t as yel heen rully studii'd. A 

 dozen species of barnacles were eninnerated 1)\' my liiend. I)i'. Tilsbi-y. from 

 the material gathered by the ship Albati-oss. But one of these, a species of 

 acorn liarnacle ^"^ ])elonging to the typical licuus of that family, was secnreil in 

 shallow water. The remainder were deep-water or olV-^hoi'c forms, most of 

 them occurring in water two or thi-ee hundred fa.thoms deep. Of the twelve 

 species secured, eight pro\-ed to be undescribed. A cai'efui study of the shore 



i« Xraipnus. i* rj/ci/xv/m. ^^ Lr/uKl'dw. i« Peduncle. ^' }i(il(i)iid,r. i'^ Balnniin aiiii>liil lili. 

 31 



