lOO Elliot, Tnhcritancc of Acquired C/iaractrrs. |l;iiuiary 



Weber Rivers in Utah. In the latter instance, it being Sep- 

 tember, the time for breeding had passed, but the birds were 

 dwelling in the holes, were frequently seen sitting in them, and 

 the author's obsei-vations led him to believe they had nested in the 

 holes, there being no trees in the vicinity. 



The evidence of variations produced by use and disuse of 

 special organs also tends to confirm our views that iicquired 

 characters are transmitted. The modifications of the wing in 

 various families of birds, when through disuse the power of 

 flio-ht has been lost, and this member has become either rudimen- 

 tarv, or else changed both in form and size so as to serve more 

 like a fin, giving its possessor additional powers for the pursuit 

 of its prey under water, are numerous ; and to attribute these 

 modifications to the principle of selection, or predisposition of 

 the germ and to deny that use or disuse has produced hereditary 

 effects, as Prof. Weismann asserts,* is to argue from a mere 

 assumption that lacks evidence to establish even its probability. 



Migration preserves a species true to its tyj^e, in that migratory 

 birds keep together in flocks, and select localities in which to re- 

 main, having similar environments to those where they were reared. 

 But if a species ceases to migrate for any cause and remains 

 isolated in its habitat, then differentiation occurs, and the variations 

 that appear are reproduced in their offspring. Thus it may not 

 be supposed that the Great Auk was always incapable of ffight, 

 but that it migrated, even if only to a limited extent, while its 

 wings were fully developed. This is a reasonable supposition, 

 because all its relatives, the Divers and Auks, are birds of great 

 wing-power and migrate at the present time. From some cause, 

 unknown to us, but possibly from its ability to procure food 

 throughout the year in the region it inhabited, it gradually ceased 

 to migrate, and its wanderings becoming less and less, its wings 

 were employed chiefly under water in pursuit of its natural food. 

 The wings therefore being used in a different manner from that 

 when the bird was flying, would be modified and reduced in size 

 until they reached the form and dimensions most suited to assist 

 the species in swimming beneath the surface, but which in their 

 reduced condition rendered flight no longer possible. These 

 modifications were transmitted to its offspring, rather, we would 



*Essays, p. 92. 



