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Mat 29th, 1885. 

 W. DENISON ROEBUCK, F.L.S., on "LIMAX MAXIMUS." 



The exhibits included parasite of Black-headed Gull, shown by 

 G. Haiusworth ; section of poplar, showing galleries excavated by larva of 

 Goat Moth {Cossiis cossits), and three larvae in cocoon, sent by G. A 

 Hobson, of Wimbledon. 



Mr. Roebuck, in his address, stated that he approached the subject 

 from the point of view of the species, as showing how much there was 

 worthy of consideration in connection with even a single organism. 

 L. maximus is a slug, the largest of the British species, and one which is 

 well distributed over the British Isles. It ranges over the whole 

 European continent as well, stopping short of the Scandinavian peninsula, 

 and giving place in Eastern Europe to such species as Limax Schwabi and 

 Limax Transylvanicus. In Italy and Southern Europe its variation is 

 great, and its allies not only numerous, but of large size and brilliant 

 colouration. The systematic position of this animal among its allies was 

 indicated, and hints given as to how best to distinguish the British species. 

 The jaws and lingual ribbons were described, and numerous specimens 

 shown under the microscope. The internal anatomy was merely mentioned 

 in passing, although it was pointed out that the reproductive organs were 

 of great value in fixing the limits of species among these animals. In its 

 habitats this slug was noted as frequenting more especially the immediate 

 vicinity of human habitations, and not so much the open country, like the 

 black and the field slugs. In respect of food, it is omnivorous, its teeth 

 being adapted to a herbivorous and refuse diet. The important subject of 

 variation was then dealt with, it being pointed out that slugs in general, 

 having their specific limits well defined by structural and anatomical 

 characters, offer a wide field for the study of colour- variation. In respect 

 of size it is difficult, without dissection, to know when a slug is adult, and 

 eight inches was mentioned as the greatest length to which this species 

 attains. In respect of colour-variation, it is to be noted that this is 

 normally an animal which has a ground-colour of light brownish ash 

 grey, with superposed markings — spots and stripes — of a much deeper 

 shade, and also with black markings. There is not much variation of 

 ground-colour recorded, except one of a lilac colour, clear and transparent, 

 and an albino. The case is different with the markings, which vary to a 

 considerable extent and degree, both by suffusion or coalescence and by 

 suppression. The typical form of Z. maximus has spots on the shield and 

 four longitudinal stripes down the body. If these stripes are sinuous 

 instead of being straight, we have the var. serpentina. If they are broken 

 in their continuity, they are var. cellaria. If still further interrupted, 

 thereby producing a series of four rows of spots instead of four continuous 

 stripes, the var. is ferussaci. If both shield and body have irregular spots 

 here and there, we get var. maculata. If the two inner bands are complete. 



