1) Regulation of lateral grafts in Hydra fusca is usually a double process of migration of the graft, and of fusion as the result of tension, i. e. the graft tends to migrate towards the head end of the stock until the head ends of graft and stock are equal in length, when fusion gradually brings them together. There is however a level of insertion somewhere in the aboral 1/5 of the stock, below which a graft will move downward and constrict off. 2) Regulation of lateral grafts in Hydra viridis is usually a process of downward migration, constriction and separation at the foot of stock. Occasionally a graft inserted very near the oral end of the stock will persist for some time and finally fuse as in Hydra fusca. 3) The difference in the behaviour of lateral grafts in Hydra fusca and Hydra viridis is probably due to a difference in the diameters of the cylinders which form them, and to the action of capillarity. 4) When two Hydras are united side by side in tangent grafts, the probability of separation or fusion as a means of regulation depends upon the area of uniting surface, i. e. upon capillary attraction. Fusion will not take place between such Hydras united with poles in the opposite direction, but if the area of union is not too large, they may swing around until the poles lie in the same direction, and then fuse into one. 5) Hydras united in end to end grafts with poles in opposite directions will not form permanent union. Hydras so united with poles in the same direction will form permanent unions if the length of the compound is less than twice that of a normal Hydra. 6) Buds may arise in a compound polyp of abnormal length within the budding zone of the compound, regardless of that of the individual components. They may also arise at the line of union. The suddenness with which they appear in these unusual places shows that their position is not long predetermined.