306 Naturalist at Large 



gaining constantly in credence among present-day students 

 of zoogeography there can be no doubt. Dr. R. F. ScharfT 

 in his History of the European Faima (London, 1 899) cites 

 many experiments to show that land snails are more easily 

 killed by immersion in salt water than many students in 

 the past have supposed. Slugs in the act of crawling on twigs 

 drop off immediately when subjected to a slight spray of 

 sea water. Scharff {loc. cit., p. 17) continues: "If we sup- 

 posed, therefore, that a slug had successfully reached the 

 sea, transported on a tree-trunk, the moisture would tend 

 to lure it forth from its hiding-place under the bark, 

 whilst the mere spray would prove fatal to its existence." 

 He adds that species of snails and slugs which lead an under- 

 ground existence would be much less likely to get started 

 on these sea voyages. The suggestion advanced by Darwin 

 that young snails just hatched might adhere to the feet 

 of birds roosting on the ground and then be transported 

 seems improbable. Dr. ScharfT in his European Animals: 

 Their Geological History and Geographical Distribution 

 (New York, 1907) states that Dr. Knud Andersen of 

 Copenhagen has informed him in a letter that he has ex- 

 amined the legs and wings of many thousands of migratory 

 birds, "that their legs were clean; and no seeds or other 

 objects were found adhering to their feathers, beaks or 

 feet. It has also been proved that birds migrate on empty 

 stomachs." 



There is also good authority for the statement that 

 amphibians and earthworms very rarely or never occur on 

 the two shores of a stretch of sea unless there is evidence 

 showing the former existence of a land connection. 



To quote again from Scharff (loc. cit., pp. 18-20): — 



