142 Bird -Lore return skirts along the railway which brought him to his place of liberation ; he is there guided by the sixth sense. Having in this way reached the known horizon, at 80 kilometers from his dwelling, for example, he ceases having recourse to the sixth sense and travels by sight straight to his own roof. Other times the Pigeon does not think of making use of the five senses on arriving on unknown ground. In this case he follows his reverse scent as far as the Pigeon cote. He passes it sometimes. We have seen him, on coming back from a long journey, pass at 40 or 50 meters from the Pigeon cote, repass it, and enter at the end of an hour or two, having perhaps crossed the wrong direction in this way from 30 to 60 kilometers. If we carry away at 10 kilometers from the Pigeon cote a Common Pigeon, accustomed to use exclusively the five senses, and a Carrier Pigeon, trained to long journeys, we will make an interesting dis- covery in freeing them simultaneously. The Common Pigeon, flying by sight, will generally make up his mind much more rapidly than the Carrier, which will take his direc- tion with care by the aid of the sixth sense. From these facts we may conclude that the sixth sense does not combine with the five others. It enters into activity in the zone where the five senses are mute, and continues sometimes to operate in the known zone to the exclusion of the other senses. It seems that it is not controlled by any impressions emanating from the route followed, and that it is in some way a subjective organ. We made, with regard to this, a very curious observation. When we transport in a railway car a basket of Pigeons having already the knowledge of travel, we see them show the greatest agi- tation when we arrive at a station where they have once been released, whilst they remain indifferent to other stopping places. Now, we will admit without much trouble, that a Pigeon shut up in a basket which, in turn, is enclosed in a dark car, cannot from the uproar tell one station from another. His sight and other senses are no help to him, since he is as completely as possible isolated from what is happening outside. However, he knows in a very exact way where he is by connecting it with his point of departure. We were then right in saying that an animal brought from a distance pos- sesses an idea about his location quite subjective, independent of the medium that he crosses at the time. We have explained that the animal lives cantoned in a domain where he meets with everything that the instinct of preservation of the individual and of the species calls for. This domain, more or less extended for the wild beast, is reduced for the Pigeon, for exam- ple, to the four walls of the Pigeon cote. Does he not indeed
