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Rh cases preceded—the body. Changes of structure, too, if slight, are not easy to see, and as soon as they become observable the varying animal is dubbed another species, or, at least, a variety of the old one, so that one is not allowed, as it were, to see the actual passage from form to form;—one is always either at one end of the bridge or the other end. But changed habits may be marked in transitu, and there is hardly, perhaps, a bird or a beast which, if closely watched, will not be seen to act sometimes in a manner which, if persisted in to the neglect of its more usual circle of activities, would make it, in effect, a new being, though dressed in an old suit of clothes. Thus, in such a bird as the robin, which is associated—and rightly—in the popular mind with the cottage, the little rustic garden, and with woodlands wild—such scenes and surroundings, in fact, as are represented, or used to be, on Christmas cards—one may get a hint of some future little redbreasted, water-loving bird, at first no more aquatic than the water-wagtail, but becoming, perhaps, as time goes on, as accomplished a diver and clinger to stones at the bottom of running streams as is the water-ouzel—a bird as to which, Darwin says, "the acutest observer by examining its dead body would never have suspected its sub-aquatic habits."

To illustrate this, I take from my notes the following:—"A robin"—it is in December—"flies on to the trunk of a fallen tree spanning the little stream, from thence on to some weedy scum lying against it on the water, from which he picks something off and returns again to the trunk. Two or three times again he flies down and hops about on the weeds,