RECENSIO CONTRADICTORIA. 



Foresight. In regard to weather. Emperor Frederic 9. Power 

 to foresee weather Brehm, Chr. L 14. — Bird Migration can be utilized 

 for weather Prognosis. Brehm, Chr. L 16. Birds possess a certain 

 presentiment of weather. Homeyer. 3. Birds have no presentiment 

 of weather. Kessler. 11. — Great sensibility. Gatke. 9. 



Guidance by experienced individuals. Exists. Weissmann. 4. 

 Exists. Martorelli. 19. — Does not exist. Gatke. 10. — Does not 

 exist. Homeyer. 8. 



Immigration or a movement to extend the range of certain species. 

 — Does not exist. Homeyer. 20. Birds undertake certain recon- 

 noitring trips. Homeyer. 25. 



Immigration has undoubtedly been observed. Zostorops lateralis 

 (Lette) immigrated from Australia to New-Zealand; the settling of 

 Serinus serinus in Silesia (valley of Hirschberg, Riesengebirge) was 

 witnessed by myself. Finsch (in litt.). 



Imperfect Migration v. Straggling p. 97. 



Impulse. — Birds of Migration are incented by an impulse, which 

 originates from straggling — imperfect Migration. Weissmann. 2. — 

 Migrating Birds follow an impulse which has arisen in the course of 

 thousands and hundreds of thousands of year. Braun. 2. — A period 

 of 2000 years has sufficed to firmly establish Migration. Parker 3. 



Instinct. Birds act instinctively. Gatke. 14. — The migratory 

 instinct depends partly on bodily, partly on traditional heredity. Palmen. 

 13. — Migration originates from an indefinable instinct. BOttner. 1. 



Mediterranean. — Migration originates in a period when the Medi- 

 terranean did not exist. Wallace. 4. The Mediterranean is passed 

 only at certain points. Wallace. 5. —The crossing of the Mediterranean 

 at certain points dates from a geological period, w^hen the Mediter- 

 ranean was divided by land into several basins. Weissmann. 6. 



tia OS ca) 



