MEANS OF DISPERSAL. 55 



The probable dispersal of bivalves while holding on 

 by closure of their shells to the toes, etc., of birds, 

 amphibia, aquatic insects, etc., remains to be dealt with 

 in the next chapter, and it will be seen that animals 

 have been secured, in a few cases, in the very act of 

 carrying the creatures over land. Dealing with 

 univalves in chapter iv., I shall have to suggest a 

 somewhat analogous mode of dispersal of operculata, 

 namely, by closure of the operculum so as to hold on 

 to insects, etc. ; and a few cases of the clinging of inoper- 

 culate univalves, by adhesion, to amphibia, insects, and 

 the like, will be added, but these latter might almost 

 have been included above, for young shells will have 

 been oftener thus carried than full-grown ones. 



