630 BIRDS. 



those liirds which do not leave the breeding area at the proper season 

 will suffer, and ultimately become extinct ; which will also be the fate 

 of those which do not leave the feeding area at the proper time." In 

 short, given environmental changes of climate on the one hand, and a 

 measure of plasticity and initiative on the part of the organism, the habit 

 of migrating would be perfected in the course of natural elimination. 



But while this view is so far satisfactory, it leaves us face to face with 

 the problem how birds migrate as safely and surely as they do on their 

 pathless way. To say that they do so by instinct only shelves the 

 difficulty, even if it were true ; and to point out that the merciless 

 elimination which continually goes on keeps up the standard of racial 

 fitness, leaves us still wondering how any became fit at all. 



One welconres therefore any suggestion as to the manner in which 

 birds learn or have learned to find their way. The power has been 

 compared to the "homing" faculty of some pigeons, but most believe 

 that pigeons are guided solely by noticing landmarks, which could 

 hardly be done over 10,000 miles of land, and obviously not over 1000 

 miles of sea, or during the night. Some have urged that birds follow 

 river valleys, the lines of old "land bridges'' connecting continents, 

 the roll of the waves, and so forth, but the difficulty remains of flight by 

 night and at very great heights. Attractive is the suggestion that birds 

 are guided by what may be called a "tradition"' based on experience ; 

 those guide well one year who have followed well in previous years. 

 But some young birds fly apart from their parents, and some birds do 

 not fly in flocks at all. Moreover, it is difficult to understand how the 

 experience could be gained except by sight, which in inany cases is 

 excluded by the darkness. In face of these difficulties, some authorities, 

 such as Professor Newton, have been led to believe that birds have, in 

 an unusual degree, "a sense of direction." 



Pedigj-ee of Birds. 



Birds have many structural affinities with Reptiles, some of 

 the ancient Dinosaurs present approximations to Birds, the 

 extinct flying Pterodactyls show that it was possible for flight 

 to be developed among Reptiles, the oldest bird — Anhceo- 

 pteryx — is in many ways a connecting link between the two 

 classes, and the development of some Birds reveals many 



remarkable resemblances with that of Reptiles, therefore 



with the strength of the general argument for evolution to 

 corroborate us, we conclude that Birds evolved from a 

 Reptile stock. 



Speaking of his work on the development of the fowl 

 W. K. Parker wrote in 186S :—" Whilst at work I seemed 

 to myself to have been endeavouring to decipher a 

 palimpsest, and one not erased and written upon again just 

 once, but five or six times over. Having erased, as it were 



