ADAMS : DISTRIBUTION OF BRITISH TESTACELLA. 2I.3 



worm-eating slugs increase and flourish when once they have found 

 a lodging in a richly manured nursery garden. 



Now it would be very extraordinary if such creatures as the Testa- 

 cellir, if native to the soil, existed only in gardens : and it might well 

 be asked where they lived before the, gardens were made. If it were 

 suggested, in answer, that the gardens were built on spots where the 

 slugs happened to be located, although (with the exception of three 

 ambiguous records) no slugs were known to exist outside gardens, 

 surely the likelihood of coincidence would be somewhat unduly 

 strained. 



It is quite true that these slugs are liable to escape notice from 

 their subterranean and nocturnal habits, and also from their protec- 

 tive resemblance to small yellow pebbles when dug up covered with 

 dirt ; that navvies breaking fresh ground are the least likely people 

 to notice such things when dug up ; that gardens are particularly 

 likely spots for close observation, and gardeners, perhaps even more 

 than ordinary conchologisls, pay close attention to slugs. 



Yet these slugs may be frequently found on the surface in the day- 

 time", crawling or feeding, and they frequently spend the day under 

 stones, flowerpots, etc., where they may be easily found like other 

 slugs ; and, considering the number of conchological observers who 

 have worked over most parts of the British Isles during the last fifty 

 years, would it not be very extraordinary if these peculiar slugs, 

 generically unmistakable to the tyro, had not been observed if they 

 existed in the wild and open country ? 



Now, when we consult Mr. Taylor's maps of ' Distribution ' — by 

 which, of course, we understand natural and not artificial distribution 

 — we find thirty-three comital areas coloured on the strength of purely 

 ' garden ' records, and we are tempted to wonder how far this cor- 

 rectly indicates the natural distribution. 



Of course it would be exceedingly difficult, and indeed often quite 

 impossible, to draw the line between records of localities where a 

 species is undoubtedly indigenous and those where it has been pos- 

 sibly introduced ; but in the case of Testacellce one would have 

 expected a warning of the possibility of artificial distribution — an 

 indirect warning, however, we have, viz., the detailed list of 'garden' 

 records. 



If these maps of distribution were intended to serve no further 

 purpose than to satisfy one's mere curiosity as to the various localities 

 where a given species might be found, these notes would have no 

 significance, but as the maps are intended to indicate, so far as may 

 be, the natural situations of species from which scientific deductions 

 may be drawn, it behoves one to guard against any disturbing factor. 



