10 96 Proceedings of the Royal Irish Academy. 



cases of presumed accidental dispersal each possibility involved is to be 

 represented by so small a fraction that, if a few of these possibilities are 

 superimposed one on the other, as in the case of Focke's hawk-slain pigeon 

 (ante, p. 81), there is hut little possibility left. One may invoke a formula 

 to express this thought ; it cannot be denied that 



A possibility x a possibility x a possibility . . . = ! 

 Even the multiplication of whatever resulting fraction there may be by the 

 big time-factor that it is permissible to draw on, will not, in many cases, give 

 us a very hopeful result. 



7. BIBLIOGRAPHY. 



List of Books and Papers consulted in the Preparation of this Paper. 



References to further bibliographies of the subjects dealt with will be found 

 below under the names Adams, Botaxy, Dcvel, Ekstaji, Elliot, Ebnst, Guppy, 

 Hemsley, Macleod, Praeger, Scharff, Schtmpeb, Sebxandeb, Yogleb. 



Adams, John : 



On the vitality of seeds buried in the soil. Irish Nat., xiii, pp. 253-255. 1904. 

 On the vitality of seeds buried in the soil Second Article). Irish Nat., xiv, 



pp. 80-82. 1905. 

 Further note on the Vitality of Seeds. Irish Nat., xiv, p. 163. 1905. 

 On the possibility of distinguishing between native and alien species of plants 

 in Ireland. Irish Nat., xviii, pp. 123-132. 1909. (Bibliography.) 

 Altum, B. : 



Zur Verbreitung der Pflanzen durch Vogel. Monatsschr. Deut. Ver. Schutz 

 der Yogelwelt, xxiii, pp. 13-17. 1898. 

 Arbeiten aus der biologischen Abtheilung fur Land- und Forstwirthschaft. 8vo. 



Berlin. 

 Babrevgton, B. M. : 



The migration of birds as observed at Irish lighthouses and lightships. . . . 



8vo. London and Dublin. [1900.] 

 The Vitality of Seeds. Irish Nat., xiv, pp. 69-70. 1905. 



Babbows, W. B. : 



Seed Planting by Birds. Report of the Secretary of Agriculture, U.S.A., 

 1890, pp. 280-285. 



Babbows, W. B., and E. A. Schwabz : 



The Common Crow of the United States. U.S. Dept. of Agriculture, Division 

 of Ornithology, &c, Bull. 6. 1895. 



