[Intercalary regeneration and segmental gradients in the extremities ofLeucophaea-larvae (Blattaria) : I. Femur and tibia].

Amputation and transplantation experiments have been made in the African RoachLeucophaea maderae Fabr. with following results: 1. Amputated leg parts will be replaced at the next moult by a small regenerate proliferating from the terminal wound. After a few moults the regenerate will have attained the length of a normal leg. 2. Even if one avoids setting terminal wounds by extirpating middle pieces out of the various segments of the leg, regeneration will occur. The extirpated parts will be replaced by a regenerate intercalated between host and transplant. Thus the normal length of the shortened segment will be re-established. 3. A gradient model is developed for the extremities which may help interpretating the phenomenon of intercalary regeneration. The gradients should have the capability of starting and stopping regeneration processes. An interruption of the gradient by an extirpation may initiate regeneration processes which will continue till the gradient step has been levelled by the regenerate tissues. The various experiments in which parts of the tibia and femur of the fore, middle, and hind leg have been combined confirm the gradient hypothesis. The experiments show that there are homologous gradients repeating in the various segments of the leg. 4. The gradient factor is strictly correlated with the proximo-distal polarity. Any direction change of the gradient is accompanied by a similar change in direction of the proximo-distal polarity of the morphologic structures. 5. In those experiments, in which the structures of host and transplant tissues were quite different, it has been shown that the intercalary regenerate as a rule has the features of that part with the most distal level in its wound area. In one set of experiments it has been shown that disto-proximal regeneration, that is regeneration of proximal parts from a distal level, may take place in the legs ofLeucophaea. 6. The regeneration capability of the femur has been demonstrated once more.