REGENERATION IN AN EARTHWORM, EISENIA FOETIDA (SAVIGNY) 1826. II. POSTERIOR REGENERATION

¹ Colby College, Waterville, Maine

Anterior substrates of E. foetida, cut exactly at intersegmental furrows, regenerated homomorphic tails at levels from 20/21 back, with no zero level posteriorly. Regenerates were hypomeric, except posteriorly and after removal of three or fewer segments, and then were equimeric or hypermeric. Heteromorphic heads, previously unrecognized in the Lumbricidae, were obtained at 34/35, 32/33, 15/16 (but only after a previous anterior regeneration). Head-like buds were formed at 16/17-19/20.

Starvation and season did not inhibit homomorphic regeneration at levels behind 40/41.

Posterior regenerative capacity in a region from 34/35 to 20/21 is characterized as bipotential, as a posterior regenerate in that region may be a homomorphic tail or a heteromorphic head.