so THE DISPERSAI, OF SHELLS. 



various countries, has never seen shells attached, and 

 Mr. O. V. Aplin, the Rev. J. C. Atkinson, Mr. Abel 

 Chapman, Mr. Cordeaux, the Rev. H. A. Macpherson, 

 Mr. T. H. Nelson, and Mr. Howard Saunders have 

 also replied in the negative to my inquiries on the 

 point. But from general considerations, and especially 

 in view of Mr. Darwin's experiment, it can hardly be 

 doubted but that very young molluscs do thus adhere 

 somewhat frequently, and perhaps the absence of obser- 

 vations made in the field is not surprising, for, as Mr. 

 Layard remarks to me, the creatures are hardly likely 

 to be noticed unless specially looked for, and this I 

 suppose is very rarely done; indeed Mr. Aplin, replying 

 that he had never seen young molluscs on the feet of 

 water-birds, carefully added that he had never looked 

 for them. Mr. F. Norgate, it is interesting to find, 

 once noticed a small grey leech clinging to the plumage 

 of a mallard shot by him. Mr. Macpherson remarks that 

 widgeon, etc., sitting all day long half awake in the wet 

 sedge, are very likely to carry shells on their feet or 

 feathers when they fly at night to their feeding-grounds, 

 and as Dr. Kobelt ^ has suggested, the creatures will 

 have a good chance of adhering also to the feet and 

 legs of herons and other birds which often stand motion- 

 less in water for hours. Even adult shells of the smaller 

 kinds may often attach themselves, but these, I suppose, 

 in most cases, are soon shaken off. Mammalia fre- 

 quenting fresh water, otters for instance, seem likely to 



^ W. Kobelt, "Fauna der Nassauischen MoUusken," 1871, 

 p. 14. 



