The fish have their own favourite places, as the birds in the hedge, and after leaving the hatch there are none for some distance. Then the brook suddenly curves and forms a loop, returning almost upon itself something like the letter 12. The tongue of land thus enclosed is broad at the top, and but two or three yards across at the bottom. There the current on either side is for ever endeavouring to eat away the narrow neck, and forms two deep pools. Some few piles have been driven in on one side to check the process of disintegration, and a willow tree overhangs the pool there. By lying on the grass and quietly looking over the brink, the roach may be seen swimming in the deeper part, and where it shallows up stream is a perch waiting for what may come down. Where the water runs slowly on account of a little bay, there, in semi-darkness under the banks on the mud, are a few tench. There are several jacks not far off; but, though they prey on the roach, it is noticeable that, unless driven by some one passing by, they rarely go into these deep holes. The jack lies in shallower water and keeps close to the shore under shelter of the flags, or concealed behind the weeds. It is as if he understood that every now and then the shoal of roach will pass round the curve--going from one pool to the other--when they have to swim through the shallower water. Sometimes a solitary fish will shift quarters like this, and must go by the jack lying in ambush. At the top of the tongue of land (which is planted with withy) another brook joins the first: this brook is very deep, and all but stagnant. In the quiet back-water here--close to and yet out of the swifter stream--is another haunt of the jack. If alarmed, he does not swim straight up or down the centre of the current but darts half-a-dozen yards in a slanting direction across the stream and hides under another floating weed. Then, if started afresh, he makes another zigzag, and conceals himself once more. At first he remains till you could touch him, if you tried, with a long stick; but at every remove he grows more suspicious, till at last as you approach he is off immediately. Jacks lie a great deal in the still deep ponds that open off the brook or are connected with it by a deep ditch; they have been known to find their way up to a pond from the brook through a subterranean pipe which supplied it with water. Those that remain in the ponds are usually much larger than those found in the stream: these are often small--say, a pound to two pounds in weight. In the spawning season, however, they come out from the ponds and go up the brook in pairs or trios. They keep close together side by side--the largest in the centre when there are three. The brook at that time seems full of jacks; and to any one who has been accustomed to stroll along it is surprising where they all come from.