140 



LIBBIE H, HYMAN 



tails being omitted). It is seen that anterior pieces usually 

 regenerate seven head segments, while posterior pieces show a 

 marked hypomerism. 



The most striking fact about the regeneration of Lumbriculus 

 inconstans is, then, that there exists an axial difference in head 



Fig. 21 Multiple outgrowths; double prostouiia. 

 Fig. 22 Multiple outgrowths; head and tail. 



formation. In short pieces normal heads tend to be formed 

 from anterior levels, but as one passes posteriorly along the axis, 

 the process of head formation is inhibited to a continually in- 

 creasing degree. 



