Born found that if the anterior half of one tadpole was united to the posterior half of the same or of another tadpole a single individual was formed which he kept alive in several cases until the time of metamorphosis. If the head of a tadpole is cut off and grafted upon the side of the body of another tadpole, the head will remain alive and continue to develop in its new position, and, if well nourished by means of the connecting blood vessels that develop, it may grow to be as large as the head of the tadpole to which it is attached. Similarly, if the tail of one tadpole is grafted upon the side of the body of another tadpole, it also continues to develop, and at the time of metamorphosis, when the normal tail is absorbed, the additional or misplaced tail also shows signs of breaking down. Even the posterior half of one tadpole, if grafted to the ventral side of another, may continue to develop, producing legs, etc. Born succeeded in uniting tadpoles of different species in several different ways. They were united by their heads or by their ventral surfaces, or longer and shorter tadpoles made by using pieces longer or shorter than a half. In all of these cases there is no regeneration at the place of union, and the internal organ, the digestive tract, nervous system, and blood vessels unite when brought into contact. When pieces are united end to end, like organs unite to like, the nerve-cord with the nerve-cord, digestive tract with digestive tract, segmental duct with segmental duct, cœlom with cœlom, and although less often, the notochords sometimes join together. The lack of union of the ends of the notochord is explained by its frequent partial displacement at the cut-end, for when the cut is made the notochord, being tougher than the other structures, is often dragged out of place in one or in both pieces, so that the ends do not meet when the pieces are put together. When like organs are brought together the substance of one unites directly with the substance of the other, and if the organ is a hollow one, as is the digestive tract or the nerve-cord, their cavities also become continuous. There is also, Born states, some evidence to show that if similar organs are not brought exactly in contact their ends find each other and unite, and if they do not at first meet squarely they may do so later. When the ends of unlike organs are brought in contact, as, for instance, the nerve-cord and notochord, they do not unite, but connective tissue develops between them. The union of like parts, Born suggests, may be due to some sort of cytotropism, the outcome of a mutual attraction between similar cells like that which Roux has observed between the isolated cells of the segmented egg of the frog. Born thinks that the first rapid union of the pieces is due to the attraction of the ectoderm of one component for that of the other. Born succeeded also in uniting pieces of the tadpoles of different