THE ROCK-BARNACLE 



6 7 



authority was decisive in his own day, and until 1830 the 

 barnacles were regarded without hesitation as a very 

 peculiar and aberrant sort of mollusks. In that year, 

 shortly before the death of the great naturalist, Cuvier's 

 interpretation of the zoological position of the barnacles 

 was upset by the publication of quite unexpected facts. 



An army-surgeon named Vaughan Thompson, who was 

 stationed at Cork, had long seized every opportunity of 

 studying the natural objects which came in his way. On 

 April 28th, 1823, after a fruitless expedition to the sea- 

 shore in search of new forms 

 of life, he chanced to throw 

 out a small muslin net while 

 crossing the ferry at Passage, 

 and made a haul of many 

 curious crustaceans. Among 

 these was one which he de- 

 scribed as a small translucent 

 animal, one tenth of an inch 

 long, of a somewhat elliptic 

 form, very slightly compressed 

 laterally, and of a brownish 

 tint. When at rest, it resem- 

 bled a very small mussel, and 

 lay on its side at the bottom of a vessel of sea-water, with 

 all its limbs withdrawn. Its shell consisted of two valves 

 hinged together along the back, and capable of opening 

 for the protrusion of the legs. At the fore end of the body 

 was a large and stout pair of limbs, provided with cup- 

 like suckers for attachment. At the hinder end were six 

 pairs of legs furnished with long bristles, which moved 

 all together, and by their sudden strokes impelled the 

 animal forward in a succession of jerks like a water-flea. 

 The tail was short and bent under the body. Through the 

 shell a pair of black eyes could be distinctly seen. It was 

 not till 1826 that Thompson discovered what this new 

 animal really was. On May ist of that year he collected 



FIG. 15. Young rock-barnacle, 

 seen from above. 



