Regeneration in acoelous flatworms: The role of the peripheral parenchyma.

1. Regeneration studies were made onAmphiscolops langerhansi,A. bermudensis, andConvoluta sutcliffei. 2. The statocyst never regenerates but can be maintained, following transplantation to a statocystless worm, at any site in the peripheral parenchyma. 3. Eyespots regenerate readily. Extra eyespots are not uncommon. 4. Regeneration of whole animals from the inner parenchyma or the epidermis, alone, was never observed. 5. Regeneration of whole animals from pure preparations of peripheral parenchyma is probable. 6. Grafts of material wholly or in large part derived from peripheral parenchyma are able to determine the appearance of new structures in the host which reflect the origin of the donor material. 7. Comparisons between acoel and triclad regeneration are discussed.