REGENERATION OF THE ENTEROPNEUST, SACCOGLOSSUS KOWALEVSKII

¹ University of Notre Dame, Notre Dame, Indiana, and Marine Biological Laboratory, Woods Hole, Massachusetts

1. Transverse cuts, which separated the animal into two parts, were made on Saccoglossus kowalevskii. When transsection occurred through the proboscis or collar region, the posterior animal fragment was capable of regenerating lost parts anterior to the amputation surface but the anterior animal portion was not able to replace more posterior parts.

2. When amputation was performed behind the branchial region, anterior parts were never formed from the posterior animal portion. However, regeneration of more posterior missing parts was now possible.

3. Regeneration occurred either from a direct proliferation of the tissues present at the amputation surface (epimorphosis) or through a remodeling of the anterior portion of the amputated fragment (morphallaxis).

4. As the locus of amputation was moved posteriorly, epimorphosis became less common and morphallaxis became the principal method of regeneration. Just behind the branchial region, successful posterior regeneration seemed to be accomplished exclusively through epimorphosis.

5. Immediately following amputation, regression often occured from the posterior fragments. If regeneration ensued, regression always preceded morphallaxis but did not precede epimorphosis.