l8o THE DISPERSAL OF SHELLS. 



Town ; ' in Australia, too, as Mr. Hedley tells me, when 

 it once obtains a footing it increases at an enormous 

 rate, until there are far more shells to the square yard 

 than are commonly seen in Europe ; in the Botanical 

 Gardens of Sydney, for instance, it absolutely swarms. 

 Some hundred living specimens of Helix neinoralis, 

 imported from England by Mr. W. G. Binney in 1857, 

 increased with great rapidity in his garden in Burling- 

 ton, New Jersey, and by 1878 the whole town was said 

 to be full of them ! '^ At Lexington, Virginia, also, this 

 snail, first noticed in 1886, probably introduced 

 accidentally, appears to have multiplied at a wonderful 

 rate; about 1889, Professor J. H. Morrison, who had 

 transplanted the creatures to several fresh places, is 

 said to have collected over four hundred specimens in 

 about an hour's time within a radius of twenty-five 

 yards. ^ Slugs in similar circumstances sometimes 

 increase with equal rapidity: in Victoria, in 1849, 

 Mr. John Carson states, a slug found in his garden was 

 welcomed as an old friend and carefully restored to its 

 feeding-ground, but by the following season " matters 

 had changed " and it was every night's work to pick up 

 " pints full ^' ; the warm, moist autumn and mild winter 

 of the region proved specially congenial, and the 

 creatures became a plague, unequalled, it is said, by 



• J. S. Gibbons, M.B., " Quart. Journ. Conch.," i. p. 367 ; W. H. 

 Rush, " Nautilus," vi. (1892), p. 81. 

 - W. G. Binney, " Terrestrial air-breathing Mollusks," v. (1878), 



P- 379- 



3 H. A. Pilsbry, " Nautilus," iii. (1889), pp. 51-2. 



