REGENERATION IN THYONE BRIAREUS LESUEUR FOLLOWING INDUCED AUTOTOMY

Abstract

1. Autotomy of the stomach, intestine and lantern with its associated structures was uniformly induced in Thyone briareus by chemical or electrical stimulation. Ninety-six per cent of the animals lived and regenerated the lost parts. 2. Although the body-wall may burst in various regions of the introvert, actual autotomy of the body-wall always occurs at the junction between the introvert and the muscular body-wall. 3. The earliest macroscopic indication of the regenerating digestive system takes the form of a continuous, rod-like thickening of the free margin of the mesentery connecting the healed anterior end and the cloaca. 4. A lumen arises within the extremities of the primary, solid rudiment. The intestinal epithelium lining the posterior section of lumen is continuous with the cloacal epithelium while at the anterior end the intestinal epithelium arises from certain masses of cells identified within the lantern rudiment. 5. The solid rudiment is progressively invaded from these two centers until 10 days after autotomy the two sections of lumen have joined to form a continuous lumen for the new alimentary canal. 6. The lantern and associated structures originate from contributions of the body-wall and more especially from the anterior extremities of the ambulacral structures. 7. A posterior half of an eviscerated or uneviscerated Thyone will regenerate all missing structures in a manner entirely comparable to that occurring within an entire animal except that regeneration of the lantern is delayed. 8. Remnants of the original intestine remaining in posterior halves cut from uneviscerated animals may become incorporated as links in the newly-formed digestive system. This has also been observed within incompletely eviscerated whole animals. 9. Anterior halves of eviscerated Thyone killed at 37 days after the operation possessed a well developed lantern with its associated structures, stomach, and intestine but no cloaca. 10. A comparison is made between the methods of regeneration found in the genera Stichopus, Holothuria, and Thyone.