RECENSIO CONTRADICTORIA. 



MANN. 2. — Straggling (imperfect Migration) sprang from Migration. 

 Braun. 3. — Migration proper (Passage) developed from wandering. 

 Weissmann. 1 2. — Migration originates from straggling (imperfect Mig- 

 ration). Palmen. 15. — Migration does not originate from strolling 

 movement, nor from heredity. Gatke. 1 3. — Strolling guests do not 

 exist. HoMEYER. 21. — The impulse of Migration is hereditary, not 

 cultivated. Homeyer. 21. (Cfr. Weissmann 12.) — Stragglers extend 

 the limits of the species and may create new routes of Migration. Pal- 

 men. 17. — Migration can give an impulse to the creation of new forms. 

 Palmen 19. — The gipsy habits of Birds are important in Migration. 

 Brehm, Ch L 1. Birds of Migration may change into sedentary Birds, 

 and vice versa, owing to conditions of food supply. Menzbier. 10. — 

 A period of 2000 years has sufficed for firmly establishing Migration. 

 Parker. 3. — It takes a long time before Migration causes a differen- 

 tiation of species. Martorelli. 16. A rather short time is sufficient to 

 produce modifications in Migration. Martorelli. 16. 



Flight of: Extremely rapid. Gatke. 6. — Not with full speed. 

 Middendorff. 2. 



Limits of: Old birds migrate farther south than young ones. Wal- 

 lace. 3. -~ Females migrate farther south. Brehm, Ch. L 11. — 

 The higher north Birds wander, the farther south they migrate for hiber- 

 nation. Seebohm. 2. — Tristram. 2. Martorelli. 15. 



Manner of: Never on foot or swimming. Homeyer. 27. — Some 

 Birds wander by walking or swimming. Brehm, Ch. L 7. 



Nature oi: Birds have an impulse for Migration and a homing 

 sense. Faber. 1. — The impulse of Migration is hereditary, not gained 

 by training. Homeyer 14, — The migratory instinct is inherited. 

 Palmen. 13. — Migration became hereditary. Martorelli. 1. Birds 

 are trained to wander. Weissmann. 4. 



Obstacles in : Migrating Birds give way before hindrances. Nau- 

 mann. 6. — Invicible hindrances cause deviation. Homeyer. Q. — 

 Hieronymus. 1. 



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