3IO KEW : THE FACULTY OF HOMING IN GASTROPODS. 



bricks of old walls, return to the same home from time to time, for 

 suitable hiding-places can only be found between certain bricks. 

 The slugs, on coming out, like limpets on rocks encrusted with fine 

 sea-weed, are generally surrounded by their food, for I am convinced 

 from repeated observations that, when living on walls, they subsist for 

 the most part on the minute lichens which give the brick or stone its 

 familiar grey and yellow-green tints. Thus they have not to wander 

 far in search of food, and I believe in many cases they spend the 

 greater part of their lives on the surface of the wall in the crevices of 

 which they shelter, and in these they are probably hatched from the 

 egg.* When no rain has fallen for a number of days, walls tenanted by 

 Limaces become literally reticulated with crossing and re-crossing 

 slime-trails. Of this I saw a striking instance while searching with 

 a lantern over the face of a stone bridge crossing a stream near Louth ; 

 the stone was ' covered ' with slime-trails, and there were more than 

 a dozen slugs {L. flaviis) within a very small area. These were imme- 

 diately over the mud usually covered with water, and there was no 

 herbage at the top of the bridge or anywhere near, except a little 

 dried-up moss, but the stone was everywhere stained with minute 

 lichens. On examining the slugs on walls and tree-trunks at night, they 

 are often observed to be busily engaged in rasping off the encrusta- 

 tion of small lichens. That the animals may become acquainted 

 with their surroundings is not, I think, in these circumstances, 

 altogether improbable. By the London Road, at Louth, where 

 large numbers of Z. inaximus live in a low wall built to retain a bank, 

 I often watched the animals in the evening squeezing out from 

 between the bricks. t On this particular wall many slugs crawl over 

 the coping and away upon the bank beyond, yet as numbers come 

 out almost every evening, it seems probable that they return to it. 

 There is evidence that slugs are able to return to special places 

 both on walls and elsewhere. On a wall at Hampstead, I saw 

 a number of slime-trails all of which appeared to start and terminate 

 at a certain hole between the bricks. The trails were very sinuous, 

 and crossed many times, so that all the journeys could not be made 

 out ; one journey to and from the hole, indicated by a distinct and 

 continuous trail, could, however, be traced with certainty. In this case 

 the slug had wandered about five feet from home. On some stone flags 



* Mr. Gude, on inserting a knife between the bricks of a wall at Hampstead, 

 impaled a very young L.flaznis. 



+ The crevices from which these slugs emerge are often very small. In 18S7, 

 I saw an individual whose body, when crawling, measured fully 14 mm. across, 

 come out from between two coping-tiles, the space between which was not more 

 than 5 mm. Immediately before, a half-grown Arion ater had come out of the 

 same crevice. 



Naturalist, 



