All the plants growing upon the surface of the earth absorb carbon. These leaves are taking up their carbon from the atmosphere, to which we have given it in the form of carbonic acid, and they are prospering. Give them a pure air like ours, and they could not live in it; give them carbon with other matters, and they live and rejoice. So are we made dependent not merely upon our fellow-creatures, but upon our fellow-existers, all Nature being tied by the laws that make one part conduce to the good of the other. AUGUSTE FOREL The Senses of Insects Auguste Forel, who in 1909 retired from the Chair of Morbid Psychology in the University of Zuerich, was born on September 1, 1848, and is one of the greatest students of the minds and senses of the lower animals and mankind. Among his most famous works are his "Hygiene of Nerves and Mind," his great treatise on the whole problem of sex in human life, of which a cheap edition entitled "Sexual Ethics" is published, his work on hypnotism, and his numerous contributions to the psychology of insects. The chief studies of this remarkable and illustrious student and thinker for many decades past have been those of the senses and mental faculties of insects. He has recorded the fact that his study of the beehive led him to his present views as to the right constitution of the state--views which may be described as socialism with a difference. His work on insects has served the study of human psychology, and is in itself the most important contribution to insect psychology ever made by a single student. Only within the last two years has the work of Forel, long famous on the European Continent, begun to be known abroad. _I.--Insect Activity and Instinct_ This subject is one of great interest, as much from the standpoint of biology as from that of comparative psychology. The very peculiar mechanism of instincts always has its starting-point in sensations. To comprehend this mechanism it is essential to understand thoroughly the organs of sense and their special functions. It is further necessary to study the co-ordination which exists between the action of the different senses, and leads to their intimate connection with the functions of the nerve-centres, that is to say, with the specially instinctive intelligence of insects. The whole question is, therefore, a chapter of comparative psychology, a chapter in which it is necessary to take careful note of every factor, to place oneself, so to speak, on a level with the mind of an insect, and, above all, to avoid the anthropomorphic errors with which works upon the subject are filled.