DISPERSAL OF SLUGS. I/I 



sibly it might be landed on one of the banks or arrested 

 by some projecting object, so as to be able to crawl away 

 in safety. Previously I had noticed that the level of the 

 water had risen rapidly, and the scum, lying, no doubt, 

 earlier in the evening stranded upon the mud at the 

 water's edge, had evidently be enfloated off with its living 

 burden by the " flood." Slugs of the same kind 

 were numerous along the muddy margins for a consider- 

 able distance. The smaller ground-slugs, no doubt, 

 like little shells of many kinds, often resort to the 

 hollow " kexes " of umbellifers, which, as already men- 

 tioned, seem likely to serve as vehicles for transportal : 

 the marsh-slug [L. Icsvis) has been noticed in the stems 

 of these plants by Mr. B. Hudson/ and I have seen the 

 field-slug (Z. agrestis) in such stems lying upon the 

 ground near a little water-course in Highgate Woods. 

 Kinds which habitually burrow into the ground and 

 spend a great part of their lives beneath the surface 

 seem likely, of course, to be occasionally transported, 

 at least in some regions, in the soil attached to the 

 roots of floating trees, but they are sure to escape, in a 

 great measure, the various accidental causes which 

 above ground bring about comparatively frequent in- 

 voluntary migrations ; thus we find Dr. Simroth re- 

 garding the Testacellce as having but little scope for 

 dispersal owing to their subterranean habits, and as 

 a consequence, he says, they have divided up into local 

 forms.' 



' " Journ. of Conch.," v. (1886), p. 48. 



= H. Simroth, " Journ. of Conch.," vi. (1891), p. 423. 



