THESES FROM LITERATURE. 



6. The crossing of the Mediterranean at certain points dates from 

 a geological period, when the Mediterranean was divided by 

 land into several basins. 



7. Birds are hereditarily gifted in a high degree with a sense of 

 orientation ; they direct their wanderings to places already 

 known to them. 



8. Migrating Birds know all the pecularities of the route and never 

 leave it voluntarily. 



Q. Migrating Birds have a fine sense for observation, sharp eyes 

 and an excellent local memory increased by experience. 



10. Migration originated, in the fact that birds settled also in coun- 

 tries which yield food only during part of the year. 



1 1. Settling took place only gradually from South to North, espe- 

 cially since the glacial period. 



12. In the course of the slow advance of the species the necessary 

 qualities for Migration itself Passage — developed gradually 

 to greater perfection 



HOMEYER, E. von: „Die Wanderungen der Vogel mit Riicksicht auf 

 die Zijge der Saugethiere, Fische und Insecten" 1881. 



1. Birds do not wander along distinct, sharply defined routes, but 

 disperse uniformly, fanlike, over extensive regions. 



2. Birds migrate essentially with the wind. 



3. Birds possess a certain presentiment for weather. 



4. Most of the small birds are crepuscular wanderers, the large 

 ones day-, and strand-birds nocturnal wanderers. 



5. Migration generally goes on at a great height. 



6. The Migration procession of each species divides itself into van- 

 guard, main body and rear-guard. 



7. Young and old Birds, sometimes also the sexes, migrate sepa- 

 rately. 



8. Guidance does not exist. 



9. Only invincible obstacles cause deviation or crowding. 



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