This is a brief exposition of the migratory habits of the alewife -- a salt water fish belonging to the herring family, which is told with enthusiasm, wonder and attention to detail. The author confined his investigation to the Cape Cod area although each year, at the vernal equinox, the alewives begin to enter innumerable inlets down the Atlantic coast from Newfoundland to Florida. Like the salmon and shad, unlike their nearest relative, the sea herring, alewives grow in salt water and spawn in fresh, their run lasting for about two months, ending in late July. Although the alewife, smoked, was once valued for its edibility and as fertilizer, now its status is as a processed food -- for dogs, cats, lobster bait and the important commercial runs extend now only from Massachusetts northward. Hay provides some interesting data on the derivation of the alewives' peculiar name and he discusses various theories of migration.