general they do tend to return to their home streams. As a proof of this, ponds that were empty of alewives have been stocked with them, and the spawn returned as adults in three or four years’ time. This is the “parent stream” theory. With salmon it has apparently been shown to be a fact; although it is not so much the stream they were born in to which they return as the stream in which they grew up. Salmon eggs have been taken out of one river, moved to another, and then the hatched fry were tagged. They migrated to the sea and returned to spawn in the second river where they had their growth. So what is to account for the alewives being able to find a “parent stream” that might be only a few yards wide, out of all the great stretches of the Atlantic coastline? They left it when they were no more than one and two-fifths to four inches long, but somehow, growing up in the sea, they must always have been oriented to that home base. They may have stayed reasonably near by, but even so this ability is hard to fathom. Disregarding the question of how they arrived at that point, how could they tell one stream from another? They enter innumerable rivers, streams, inlets, some of them in close proximity. One theory has it that they are able to find their home waters by their characteristic odor, their special composition, to which they were conditioned when young. Even so, how did they get there? How can fish way offshore in waters of a consistent temperature, without any landmarks, tell which direction will take them to their home street? It is quite likely that they would be able to detect the outlet waters where they merged with the sea, but a stream may not reach very far, perhaps a few hundred yards or more at low tide, before being totally absorbed. All the way along the coasts, rivers and streams pour in fresh water, mixed in the estuaries so that it is brackish when it reaches the sea. The sea water increases in salinity as it gets deeper over the continental shelf. An alewife may detect very slight differences in salinity comparatively far out, but we are still not much closer to realizing how it finds its way.