220 LIFE BY THE SEASHORE. 



There are few more beautiful sights than a rock covered 

 with acorn-shells exposed to dashing breakers. The moist 

 oxygenated air seems to excite the little creatures, and they 

 open almost before the first drops touch them, and keep up 

 their vigorous fishing till the last drop trickles off the rock. 

 The sight of those myriads of little fans in action is one not 

 soon to be forgotten. The acorn-shells have another interest 

 in their history. They were long thought to be molluscs, 

 and it was not till, in 1830, their development was fully 

 worked out by J. Vaughan Thompson, that their true 

 position was understood. 



The details of the anatomy are somewhat beyond our 

 scope, but we may notice that the segmentation of the 

 body is quite indistinct, and that it is clothed in a fold of 

 skin, which secretes a shell of limy plates. The limy plates 

 consist of a ring fixed to the rock and inclosing the body, 

 and a movable lid or operculum, formed of separate plates, 

 which open to allow the protrusion of the six pairs of two- 

 branched jointed feet. The commonest species is Balanus 

 balanoides, but there are several others on our shores. 



An even more curious creature is the related ship-barnacle, 

 Lepas anatifera, occasionally found on wreckage on the 

 shore. It has a long fleshy stalk, usually several inches in 

 length, bearing at its tip a complicated whitish shell, and 

 attached to floating wood by the other end. The shell is 

 formed of five separate plates, and in life is continually 

 opening at its tip to allow the six pairs of jointed legs to 

 be protruded. The ship-barnacle has some antiquarian 

 interest, because it was thought by the old authors to have 

 some connection with the Bernicle Goose. The old herbalist 

 Gerard described the young geese hatching out of the 

 barnacles under the influence of sunlight, but though there 

 are very many strange things about these curious creatures 

 there is nothing quite so strange as this. 



Two more of the lower Crustacea must be briefly described, 

 not because they can be studied with any degree of success, 

 but because they are certain to be encountered. These are 

 two parasites, which are true Crustacea in their youth, but 

 in adult life display no trace of Crustacean characters. One, 

 PeMogaster paguri, is very common on the hermit-crab, the 

 other, Sacculina carcini, is found on the abdomen of the 



