everywhere well known. As the result of this collaboration, the 
migratory route of the stork in Europe has been established with 
considerable acuracy. 
Palmen The efforts of Sundevall and Peters were fol¬ 
lowed in 1876 by the masterly work of Pal¬ 
men of Sweden who determined the migratory route of nineteen 
species of European birds. Palmen emphasized the fact that birds 
do not travel in a “broad front” as suggested by von Middendorf 
but that instead each species moves in a definite path or route of 
its own. 
Cooke About 25 years ago the U. S. Biological Sur¬ 
vey began a systematic collection of data con¬ 
cerning the movements of migratory birds in North America and 
already several most valuable papers, based upon the abundant 
data thus being collected, have appeared from the pen of Mr. W. 
W. Cooke, who is in charge of these admirable investigations. 
Meanwhile speculations have multiplied far in advance of facts. 
It goes without saying that satisfactory explanations of the laws 
governing bird migration can only be hoped for after a far greater 
basis of facts has been established. However, speculations and 
theories of bird movements, unsatisfactory as they are, possess a 
certain interest, not to say value, as indicating the progress of 
science along this line of investigation. These guesses at the truth 
may accordingly be grouped as the answers to two questions: 
first, how do birds find their way in migration, and second, why do 
birds migrate? 
I. How do Birds Find Their Way in Migration? 
In«tinct Theory To say that birds find their way instinctively 
is only a roundabout method of acknowledging 
that we do not know what the mechanism of migration is. The 
term “instinct” is a vague generalization which, being made to ap¬ 
ply to many diverse phenomena, loses its value in any particular 
case. Moreover the instinct theory not only does not explain any¬ 
thing but, since it does not admit of experimental test, closes the 
door upon the hope of ever reaching a satisfactory explanation of 
the phenomena to which it is applied. 
MagnetUm Theory ^^55 ^on Middendorf, to whom reference 
has already been made, advanced the novel the¬ 
ory that birds are guided by lines of terrestrial magnetism which 
cross in the body after some such fashion as in a solenoid. This 
speculation Is interesting because there Is no known fact what¬ 
ever in support of it. There are, however, facts against It. In 
North America, for example, birds do not go toward the magnetic 
