So I walked the sea lands, following the alewives’ avenue of approach. Well beyond the weir I began to get in too deep to qualify as an investigator. I judged that the brackish water of the outlet went at least five hundred yards out, and probably several hundred yards more than that, before it flowed into the salt waters of the Bay and then was lost in them. It seemed, during low tide at least, that the alewives might detect the fresh water reasonably far out in the Bay, disregarding the question of how they arrived at that point. As I went back across the wind again, under the hovering, crying birds, and saw where the waters of the two creeks came out, that strange fish knowledge of where to go was still unbelievable. I imagined alewives coming in here, or to a shore where there were even more creek inlets fairly close together, and wondered whether the schools joined in the Bay like concentric circles and then separated, each going to the stream in which it grew up. I also wondered about that supposed chemical sense, or sense of odor, that might explain the alewife’s knowledge of its home stream. Would not the composition of the waters of any one stream change greatly at various times of the year? It must be very different in the hot summer, when the little alewives come down to salt water, from the cool months of spring when the adults came in. Would that not be just as important a factor as the stream’s difference from another close by? Two miles farther up along the shore is another inlet at the mouth of Sesuit Creek. Many years ago the Sesuit and Quivett inlets were interconnected at some point back in their tidal marshes; and before the roads and banks were built that now divide them there was also more access to several ponds in the vicinity, both large and small. Since the glacial ponds of Cape Cod seem to fill up and dry out in time, turning to wooded or grassy hollows, it is possible too that the alewives had even more entryways, and went even farther inland, having longer fresh-water routes to travel--water veins open and flowing everywhere. In any event, the alewife population now starting up these two inlets is very small compared to that of Stony Brook, which shows that the fish are balanced in numbers according to the relative ease or difficulty of getting inland to adequate spawning grounds. In part, it also seems to be an added proof of the parent stream theory. The fish know their way. For whatever reason, and whether or not they are entirely consistent in coming back to the exact stream, it seems to us that they have a remarkable sense of direction, although, for all we know, it may not be any more remarkable than the accuracy of the tides or the timing of the sun. VIII The Common Night