So the alewives did not choose to come in by night or evening only, seeing that they chose to come in by day--provided there was much choice in the matter. I heard the theory put forward that they must have been chased in by bass; but if they were so chased, it did not seem likely that they would choose the narrow waters of this particular creek for refuge, or have that much calculation in them. That is not why they came in. Those thousands of years the alewives had migrated provided their own track. The fish knew instinctively when and where to go, and all risks were incidental to that. The only possibility was that they might have been schooling around in the farthest reaches of the creek waters in the bay and were hurried in by the bass; but they were there first. Many others may have gone in the night before. Those trying to come in during the morning waited their turn after an ebb tide. This rhythmic deliberation and then going seemed very characteristic of the fish as I had watched them in inland waters, and in a larger way it might be similar to their schooling in salt water. I found out subsequently that the alewives coming into the Bournedale run in the Cape Cod Canal do so both day and night, but that there is less chance of the gulls intercepting them there because of the deeper waters. I went down to Paine’s Creek the following morning, May 22, and the frenzied hunt was going on again. I had checked the previous night and did so the night of this day too and there were no fish coming in, so far as I could tell. There was no sign of them in the water during the late evening, no sound of their soft slapping on the surface later on. It is my impression that though they start into the creek in the dark--perhaps not later than ten-thirty or eleven o’clock--they do not move upstream very much until daylight comes. Sunlight stimulates them, or, to be exact, its radiation. You can see them swimming up faster in Stony Brook after the bright sunlight warms the water in the morning. They might enter the creek more successfully under the protection of fog, or darkness, combined with deep water, but did not prefer such conditions to broad daylight. When the temperature was right and they were physiologically ready, alewife schools began to move in from salt water on an incoming tide ... swing in might be a better term, since a circular movement is characteristic and sends them on. According to my observation, incidentally, this is very likely to be counterclockwise. In any case the power and direction of the migration came from their combined rhythmic impulses.