The Migration of Fishes. 29 
Seis iene et a 
come near the shore only in dead of winter, though abundant in 
summer on the edge of the outside banks in 80 to 300 fathoms 
of water. The sand-dabs (Hippoglossoides dentatus) are abundant 
in July, in water of 60 and 80 fathoms, ten miles off Cape Ann. 
In the middle of winter they swarm upon the sand-flats in water 
of 2 or 3 fathoms depth. 
Ill NOMADISM AND EQUATORIAL MIGRATION. 
The Spanish mackerel, the bonito, and the tunnies are 
good examples of nomadic species. In summer they throng 
our northern waters; in winter they are under the tropics. 
Others, like the sea-herring, appear to migrate in two ways. 
Their movements are approximately both parallel with and 
vertical to the coast-line ; that is to say, they secure changes of 
temperature both by leaving the upper strata of the ocean, and 
by moving toward and from the south. The researches of 
Boeck in Norway show that the schools approach the coast by 
gullies or submarine valleys from the oceanic depths. Such 
is doubtless the case on our coast, in their earliest ap- 
proaches, though having reached the shallows near the shore, 
the schools range along great stretches of coast-line. Since 
fishes have no restrictions upon their movements, except 
those of food and temperature, all active species must tra- 
verse areas of many hundreds of miles during the year. 
IV. THE VIEWS OF RECENT INVESTIGATORS. 
The tendency of all the researches made during the past 
few years have been to confirm the views advanced by Pro- 
fessor Baird, in an unpublished letter, written in 1873, to the 
Hon. Hamilton Fish, Secretary of State. “The question in 
regard to the migration of fishes is one that has attracted 
the attention of both fishermen and naturalists for many years 
