the line of its course winds round and around the trunk of the tree. This last, however, has not been quite my experience. I have watched the bird often and carefully, and I should say that a true spiral ascent by it is decidedly exceptional. Often one has alighted upon the tall stem of a Scotch fir, on the side away from me, and never come round into view at all. On other occasions, after some time, I have seen its tiny form outlined against the sky on one or other side of the trunk, considerably, higher up, and then, again, it has disappeared back, or flown to another tree. This can hardly be called a spiral ascent, and I have seen no nearer approach to one. Often, too, I have seen it mount quite perpendicularly for a considerable distance. To me it appears that the tree-creeper recollects, occasionally, that he ought to ascend a tree spirally, and begins to do so, but the next moment he forgets this tradition in his family, and creeps individually. One might expect, indeed, that insects or likely chinks for them would act as so many deflections from the path of spiral progress, which, as it seems likely, may have been originally adopted for the same reason and upon the same principle that a road is made to wind round a mountain instead of being carried up the face of it. But how is it, then, that the wren and the blue-tit ascend tree-trunks perpendicularly? for one would have thought that the less au fait a bird was, the more would the advantages of an easy gradient have forced themselves upon it. But these birds are still—sometimes, at any rate—aided by their wings, so that it would seem as though their tree-creeping had been developed, or was being developed, as an adjunct to
