no difficulty, but that paper separated therefrom by a space was an insuperable obstacle. Professor Pérez has pointed out that this is no doubt due to the large space offered to the bee, which consequently moves about, and does not concentrate its efforts on a single spot, as it of course is compelled to do when confined in its natural cell. The power of the mason-bee to find its nest again when removed to a distance from it is another point that was tested by Du Hamel and recounted by Réaumur. As regards this Fabre has also made some very valuable observations. He marked some specimens of the bee, and under cover removed them to a distance of four kilometres, and then liberated them; the result proved that the bees easily found their way back again, and indeed were so little discomposed by the removal that they reached their nests laden with pollen as if they had merely been out on an ordinary journey. On one of these occasions he observed that a _Chalicodoma_, on returning, found that another bee had during her absence taken possession of her partially completed cell, and was unwilling to relinquish it; whereupon a battle between the two took place. The account of this is specially interesting, because it would appear that the two combatants did not seek to injure one another, but were merely engaged in testing, as it were, which was the more serious in its claims to the proprietorship of the cell in dispute. The matter ended by the original constructor regaining and retaining possession. Fabre says that in the case of _Chalicodoma_ it is quite a common thing for an uncompleted cell to be thus appropriated by a stranger during the absence of the rightful owner, and that after a scene of the kind described above, the latter of the two claimants always regains possession, thus leading one to suppose that some sense of rightful ownership exists in these bees; the usurper expressing, as it were, by its actions the idea—Before I {39}resign my claims I must require you to go through the exertions that will prove you to be really the lawful owner. Another experiment was made with forty specimens of _Chalicodoma pyrenaica_, which were removed to a distance of four kilometres and then liberated. About twenty of the individuals had been somewhat injured by the processes of capturing, marking, and transferring, and proved unable to make a proper start. The others went off well when released, and in forty minutes the arrivals at the nest had already commenced. The next morning he was able to ascertain that fifteen at least had found their way back, and that it was probable that most of the uninjured bees had reached home; and this although, as Fabre believed, they had never before seen the spot where he liberated them.