70 ECOLOGICAL FOUNDATIONS OF ZOOGEOGRAPHY 



addition to arboreal snails, the strand-inhabiting Auriculacea are 

 especially exposed to such transport. 



In any case, the assumption of a large role for such rafting in the 

 colonization of a given territory must be made with reservations. In 

 general, the chance nature of raft transport would result in a varied 

 assemblage of animals, unrelated except for the common adaptation 

 for this means of dispersal. Pilsbry 64 and Crampton 05 regard the land 

 snails of the Pacific Islands as spread by land connections rather 

 than by fortuitous dispersal, on account of the common primitive 

 characters of kidneys and genital organs of the genera Tornatellina, 

 Pupa, Partula, and others. Some authors similarly regard the placental 

 fauna of Australia, with the exception of the dingo, as non-fortuitous, 

 since there are 6 genera of rodents, with 50 species. 66 If these 6 genera 

 of mice form a related group, however, they might well be the result 

 of a single landfall; and the absence of other forms is then exactly 

 in accord with the requirement of a "chance" assemblage by fortuitous 

 dispersal. 



The dispersal of living terrestrial forms by flying animals must be 

 a rare occurrence. Pseudoscorpions, among others, have been found 

 attached to flies, crane flies, beetles, and bugs; it is highly unlikely 

 that they are in any way parasitic, and it may be supposed that in 

 some cases they had attached themselves in search of parasitic mites. 67 

 It is, of course, entirely natural for parasitic forms to be carried in 

 this way. The nest parasites of swallows and swifts, for example, are 

 transported by their hosts, and still more the feather and hair mites, 

 and lice, fleas, and parasitic Diptera. The same is true of the minute 

 external parasites of bees and ants. 



Intentional and unintentional transport by man has carried great 

 numbers of animals to countries where they were originally absent. 

 Domestic animals were taken with him, and then frequently became 

 wild; horses and cattle in the various parts of South America did so, 

 cattle in Australia, pigs and goats on many islands. Primitive peoples 

 did this as well as civilized man. The wide distribution of pigs in the 

 South Sea islands is explained in this way, and the presence of the 

 dingo in Australia is also attributed to the agency of man. 68 Seafarers 

 have often left domestic animals on isolated islands as a source of 

 food for later visitors. By this means cattle were introduced on St. 

 Paul, rabbits on Porto Santo and Kerguelen, and goats on Juan 

 Fernandez. 



Game animals have been similarly transported and established in 

 new localities. The fallow deer was introduced in central Europe from 

 the Mediterranean province. There has been a great waif transporta- 



