46 THE DISPERSAL OF SHELLS. 



the point appear to be required, but I can hardly think 

 that anything other than negative results will be 

 obtained/ Four warty- newts, placed in a vessel of 

 water by Mr. C. Robson, extruded a number oi Pisidia, 

 the shells of most of which were open, with the animal 

 extracted ; four, however, were closed, and three of 

 these contained young ; the adult animals had been 

 extracted even from these closed shells, but, in 

 some of the young, the animals were still within the 

 shells, yet it does not appear that they were actually 

 observed to be alive." As far as diffusion by animals is 

 concerned, it seems clear, I think, that the creatures arc 

 chiefly carried while very young, adhering to the feet 

 and feathers of aquatic birds, or attached to plants thus 

 adhering. Adult and partly grown shells, however, are 

 liable to occasional transportal by creatures of various 

 kinds, and, through the agency of birds, adult bivalves, 

 even some of the larger kinds, may sometimes be carried 

 through considerable spaces ; but before giving the 

 facts on this head we will consider the possible dispersal 

 of fry and ova. 



Mr. Darwin has a statement at page 344 of the 

 " Origin " that the eggs are not likely to be transported 

 by birds ; but Mr. Wallace, Professor Tate, Lieut.-Col. 

 Godwin-Austen, and other writers have referred to 



1 The eggs of Liuincca auncularia^ it has recently been stated, 

 have passed unharmed through the digestive system of swans. 

 See " Zoological Record,'' xxviii. (1891), Moll. p. 37, referring to 

 Pascal, " Journ. de Conch.," xxxi. pp. 9-15. 



' C. Robson, " Science Gossip " for 1875, P- 220. 



