If you say the “anadromous habit” started somewhere in geologic time, it is difficult to conceive of, and it is probably not accurate, in the sense that these adaptations to environment do not start so much as develop and evolve. In any event the incredibly long history of the earth is not broken down with any facility. First of all, leaving out the question of whether fish originally evolved in fresh waters or the sea, and then blithely skipping one hundred million years or so, you have an evolved race of alewives, established residents of the sea. As to their habit of spawning in fresh water, it is possible that alewives, like other coastal fish, may gradually have explored the inland rivers and streams, until they began to use their comparative quiet and refuge in which to spawn. Along the northern coasts their inland migration would have been interrupted during the glacial epochs, and their range would have started farther to the south. There are landlocked varieties of alewife in Lake Ontario and in New York State, which also suggests a period when the continental glaciers retreated, leaving an access by water to inland lakes from the sea which was later cut off. In any case this anadromous habit was arrived at gradually, involuntarily, over a very long time. But, in a sense, what you see _now_, your center of history, is a routine which is neither old nor new but both various and inexorable, having in it the pull of the land, the blood of the sea. This starting, circulatory movement of the few small schools I had seen was succeeded by the swimming of steady herds in the brown water of the channel. I couldn’t find them at first. On the ebb tide, when the water had receded enough from the banks along the inlet I walked there for a while and then cut across the tidal marsh. The day was cool and fresh, with a light northeast wind lifting in, and it smelled of the sea. (You can live a mile or so inland on the narrow peninsula of Cape Cod, in the towns or oak woods, and never smell that rich combination of salt water, shellfish, and tidal marsh, unless the wind is from the right quarter, with a special condition of the atmosphere.) Light rippled up the broad inlet--the coppery waters seemed to move slowly and reliantly. The season had hatched its enthusiasms everywhere, from flies, to crabs, to birds. The tidal ground was pitted with holes made by fiddler crabs. They backed away in front of me, the males comically holding up their one big claw--little characters of a dull metal-blue, with bubbling mouths--and disappeared into the safety of their burrows. Ahead of me nine Canada geese, which had been resting and feeding in the marshes, unfolded their wings and lunged up and out toward the Bay.