300 Shell Life 



foot exudes a very adhesiv^e mucus, and it is conse- 

 quently difficult to dislodge the slug, which appears 

 almost to be part of the plant it feeds upon. It is a 

 remarkable example of the economy of nature when 

 the food serves at once to nourish a creature and to 

 provide it with that protective coloration which 

 renders it invisible to its enemies. In experiments 

 made with this species by Mr. W. Garstang, the slugs 

 refused even to walk over or rest upon red weeds 

 provided for them, no doubt realising by some sense 

 that such a contrast made them too conspicuous. 



Alder's Slug {Alderia Qiiodesta) was discovered 

 nearly sixty years ago by Professor Allman, and 

 dedicated by him to one of the authors of the 

 magnificent "Monograph of the British Nudi- 

 branchiate Mollusca." It is remarkable as being 

 almost amphibious. Strictly speaking it is not a 

 Sea-slug, but a salt-marsh slug, as will appear best 

 by a perusal of Professor Allman's account of its 

 discovery near Skibbereen, in County Cork, in a salt- 

 marsh that was only covered by the highest of 

 spring-tides. He says : " The day Avas bright and 

 warm when I met with this curious little animal. 

 ]\[any had crept out of the water, and were crawling 

 over the moist fronds of Enteroinorplia intesthicdis, 

 and seemed to delight in exposing their slimy bodies 

 to the influence of the warm autumnal sun. Others 

 swarmed on the mud in the little shallow pools of 

 the marsh, when their ova were abundantly de- 

 posited in the usual gelatinous masses characteristic 

 of the eggs of the nudibranchiate gasteropods, a 

 fact which is of itself sufficient to prove that this 

 strange semi - marine and even semi - aqueous habit 



