Aberrent regeneration in carcinogen-treated earthworms (Eisenia foetida).

Groups of earthworms (Eisenia foetida) were injected either with 1% methyleholanthrene (MCA), 0.5% 7–12, Dimethylbenz (a) anthracene (DMBA) or 3 × 10−4 mg of N-methyl-N-nitrosoguanadine (NMNG), After one week, the posterior ten segments were removed from all worms. Twenty-five days after amputation the mumber of regenerated segments were counted. A statistically significant overgrowth of segments occurred in MCA-treated worms as compared to controls. DMBA treatment failed to alter the mumber of regenerating segments and worms treated with NMNG had statistically fewer regenerating segments than controls. An overgrowth of segments also occurred in certain groups of vehicle-injected control worms. The groups receiving oil-based vehicles had significantly greater growth than Hank's Balanced Salt Solution injected controls. A new theory of the mechanism of regeneration is offered to explain the seemingly paradoxical results.