In some of the lower animals, for example the ants, the sexes differ remarkably from each other and appear to belong to different zoölogical families. The eyes, the form of the head, the color, and the whole body differ so much that, when a case of pathological lateral hermaphrodism is produced (that is, when the sexual glands are male on the one side and female on the other), we can exactly determine the male or female character on each portion of the body. We thus see hermaphrodite ants with one half of the body male and the other half female--black on one side and red on the other, a large eye on one side and a small eye on the other, thirteen joints in one antenna and twelve in the other, and so on. In this case the mental faculties are sometimes female, sometimes male, according as the ecphoria of the brain is influenced by the hereditary mneme of the male or female part of the hermaphrodite sexual organs, which results in a male or female brain. I have seen hermaphrodite ants in which two parts of the thorax formed a crossed hermaphrodism; in front, male on the right and female on the left, behind female on the right and male on the left. Further; among ants which live in societies, the progressive transformation of the species, or phylogeny, has produced a third sex derived from the female sex--the worker; sometimes there is even a fourth--the warrior. In these two forms the wings are absent, but the head and brain are much larger; the sexual organs remain female, but are very small. While the large brain (pedunculated bodies of the supra-esophageal ganglion) is almost rudimentary in the male, it is well developed in the female and very large in the worker and the warrior. Among these singular animals exist pathological hermaphrodites, not only between males and females, but between males and workers, and not only lateral but mixed and crossed in all possible ways. I have seen a hermaphrodite, whose abdomen and sexual organs were almost entirely male, accomplish all the complex instinctive actions of a worker of his species (expeditions, attacks on a hostile ant heap, abduction of chrysalids), thanks to its head and brain which were of the worker type. The female itself is incapable of such complex actions. I cite these facts here as material for study, for we are only too prone in this domain to generalize prematurely and to draw too hasty conclusions. In reality, there is still a wide field for study of the greatest interest. There are animals which are normally and physiologically hermaphrodite, for they possess in the normal state male and female sexual glands and fecundate themselves, such as the solitary worms, or in pairs such as the snails. In the latter case there is copulation, during which each animal plays the parts of both male and female.