and unusual delays in the migration movement are all directly 
traceable to the barometric conditions prevailing ai the time. 
Marek’s observations begun upon the woodcock were extended 
to very many other species. In fact, the paper referred to is a 
summary and generalization of 43 papers bearing upon migration, 
which this industrious investigator has published. It must be ad¬ 
mitted that Marek’s theory has the great advantage of dealing 
with known factors which may be made the object of further in¬ 
vestigation. From his point of view there is no necessity for re¬ 
ferring the habit of migration to hypothetical ancestral behavior, 
nor for endowing birds with such human attributes as love of home 
or the memory of previous successes. The streaming northward 
of birds in the spring and their return southward in the fall are 
both primarily dependent upon the same observable external fac¬ 
tors as those which cause the flow of the air in the form of pre¬ 
vailing winds, northward in the spring and southward in the fall 
Conclusion riddle has by no means been solved. 
There still remains an immense halo of mystery 
around bird migration because there are so many things we do not 
know. We not only do not know zvhy birds migrate but as yet 
we do not know hozv they migrate except in a general way. 
What becomes, for instance, of the swallows, has been a conun¬ 
drum for 2,000 years. Aristotle thought that swallows passed the 
winter buried in mud or in the bottom of ponds. Linne credited the 
hibernation idea. Dear old Gilbert White, in spite of his observ¬ 
ing eye, died in doubt. Finally, a few decades ago an Italian nat¬ 
uralist thought it worth while to submerge a few swallows under 
water to see how long they would survive. These feathered mar- 
tvrs to science of course promptly died, and thus at least there was 
delivered the death blow to the hibernation-under-water theory, 
but to this day no one knows the complete migratory route of the 
swallows nor where they pass the winter. Mr. Wells W. Cooke, 
our American authority upon bird migration, writes; “Upon leav¬ 
ing the Gulf of Mexico did they drop into the water and hibernate 
in the mud as was believed of old, their obliteration could not be 
more complete.” 
The meagerness of our knowledge concerning the migration of 
swallows is repeated to a large extent in the case of almost every 
other species when we seriously attempt to winnow out fact from 
fancy. It may, therefore, be said in conclusion that, until the store 
of facts as to how birds migrate has been greatly increased, we 
can only delight ourselves with interesting speculations as to zvhy 
birds migrate, acknowledging the problem unsolved. 
