REGENERATION 175 



of the influence of the regenerate on the stump which was so 

 characteristic of total regeneration. In the present case, re- 

 generation is not followed by morphallaxis. Whereas in total 

 regeneration, all interest was focused on the influence of the 

 regenerate on the fragment, here, in contrast, we must study 

 the influence of the stump on the regenerate. 



First of all, it appears that the differentiation of the re- 

 generate is governed by the stump of the amputated organ, 

 and not by influences originating in the body as a whole. Fore- 

 limbs have been grafted into the place of a hind-limb, and 

 amputated after some time. In such cases a fore-limb was 

 regenerated on the stump. If the limb had been rotated during 

 transplantation (e.g., implanted upside down), the orientation 

 of the regenerate agreed with that of the stump, and not with 

 that of the body (Weiss, 1924). We have already seen (p. 151) 

 what will happen if a limb or tail is extirpated completely and 

 no stump left at all: no regeneration takes place in this case. 

 This led Guyenot (1927) to the formulation of the concept of 

 "territoire de regeneration''. For each part of the body, a certain 

 region can be indicated within which regeneration of this part 

 can take place ; if this region is removed completely, no regenera- 

 tion occurs. Within the region, the formation of the part in ques- 

 tion can even be induced by local stimulation, e.g. by an out- 

 growing or regenerating nerve. If a nerve of the hind-leg (nervus 

 ischiadicus) in amphibians is diverted under the skin in the 

 vicinity of the fore-limb, a supernumerary fore-limb is formed 

 there. If diverted under the skin of the tail, it causes the forma- 

 tion of an extra tail (Guyenot, 1928). 



The fact that the organs developing in the regenerate are in 

 direct connection with the remaining organs of the stump 

 might lead to the assumption that the former originate simply 

 as outgrowths of the latter. In other words, each tissue that is 

 exposed in the wound would grow out into the regenerate, and 

 in this way the replacement of the missing part would be 

 brought about by the co-operation of the organs. The following 

 experiments disprove this view. Weiss (1925) extirpated the 

 humerus from the fore-limb of a newt, and a little later 

 amputated this limb in the upper-arm region. No skeleton was 



