DISPERSAL OF SLUGS. 169 



in a thin transparent capsule formed of the hardened 

 mucous secretion of the animal's skin. The body was 

 contracted, and oval in shape, but it had been so 

 completely protected from evaporation that there was 

 no noticeable reduction in bulk after these hottest 

 months of the year, during which water had been 

 entirely withheld. One or two specimens had died 

 almost immediately after capture, and a few escaped, 

 so that all those which had been exposed to the heat 

 and dryness in the box had become encysted, and sur- 

 vived in apparent health." ^ 



Slugs in such a condition at the roots of trees, etc., 

 would be nearly as well fitted for dispersal as snails, at 

 least by fresh-water currents. 



Slugs of most sorts and the eggs of some kinds must 

 certainly be carried to short distances within given land- 

 areas with some frequency ; various means, organic and 

 inorganic — probably of kinds already suggested— operate 

 no doubt to bring about short involuntary migrations. 

 River agencies must have widely scattered the creatures. 

 Some are arboreal, inhabiting old and decaying trees 

 which, when blown to ground, or washed out of river- 

 banks, must sometimes be carried off by floods. In our 

 own country we find slugs — the great grey kind, Limax 

 viaximus, for instance — living under the bark of old 

 willows by river-sides. At times, too, we find them well 

 concealed in chinks and among debris in the interior of 

 hollow trees, and, like some snails, they probably eat 



' E. B. PoLilton, ^' Nature,'^ xxxiv. (1886), p. 618. 



