70 PROTECTIVE COLORATION 



CHAP. 



in Cornwall are banded with rings of colour, especially with 

 black and white, in a more varied and striking way than any 

 other specimens that have ever occurred to my notice. I am 

 inclined to refer this peculiarity to a tendency towards protec- 

 tive coloration, since the rocks on which the Purpura occurs are 

 often banded with veins of white and colour, and variegated to 

 a very marked extent. 



Ovula varies the colour of its shell from yellow to red, to 

 match the colour of the Crorgonia on which it lives. The same 

 is the case with Pedicularia, which occurs on red and yellow 

 coral. 



Helix desertorum^ by its gray-brown colour, harmonises Avell 

 with the prevailing tint of the desert sands, among Avhich it 

 finds a home. Benson observes that the gaudy H. haemastoma, 

 which lives on the trunks of palm-trees in Ceylon, daubs its shell 

 with its excrement. Our own Buliminus ohscurus, Avhich lives 

 principally on the trunks of smooth-barked trees, daubs its 

 shell with mud, and must often escape the observation of its 

 enemies by its striking resemblance to the little knots on the 

 bark, especially of beech trees, its favourite haunt. Some 

 species of Microj^liysa^ from the West Indies, habitually encrust 

 their shells with dirt, and the same peculiarity in Vitrina 

 has already been mentioned. Ariophanta Dohertyi Aldr., a 

 recent discovery from Sumatra, is of a green colour, with a 

 singularly delicate epidermis; it is arboreal in its habits, and is, 

 almost invisible amongst the foliage.^ Many of pur own slugs, 

 according to Scharff, are coloured protectively according to their 

 surroundings. A claret-coloured variety of Arion ater occurred 

 to this observer only in pine woods, where it harmonised with 

 the general colouring of the ground and the pine-needles, while 

 young winter forms of the same species choose for hiding-places 

 the yellow fallen leaves, whose colour they closely resemble. 

 Limax marginatus (= arhorum Bouch.) haunts tree trunks, and 

 may easily be mistaken for a piece ot bark ; Amalia carinata 

 lives on and under the ground, and in colour resembles the 

 mould ; Arion inte7'medius feeds almost exclusively on fungi, to 

 which its colour, which is white, gray, or light yellow, tends to 

 approximate it closely ; Greomalacus maculosus conceals itself 



1 Nautilus, vi. 1892, p. 90. 



