232 



CHAPTER XXXVII. 



KNOWN TOO WELL. ONCHIDIUM. AKION. — GEOMALACUS. — LIMAX. — DE- 

 PREDATIONS. — THE TREE SLUG. TESTACELLA. 



SLUGS. 

 ONCHIDIAD^, LIMACID^, TESTACELLIDiE. 



OuE comparatively limited knowledge of the first of these 

 famiHes is amply and painfully compensated by an experi- 

 mental acquaintance with the second. While the former 

 consists of air-breathing slugs, which nevertheless must live 

 in a position accessible to sea-water, the latter everywhere 

 pervade our gardens, cellars, trees, and fields. 



The Onckidiadce are represented in the British Pauna by 

 one genus and species only, the 



Onchiditjm Celtkum, which lives in company, on the per- 

 pendicular sides of rocks, ascending or descending with 

 the tide, so as to keep a distance of about a foot above the 

 surface of the water, thus avoiding immersion, while the 



