TISSUE AFFINITY IN AMAROECIUM. II. REAGGREGATION OF THREE PARTIAL ZOOIDS INTO FUNCTIONING SIAMESE TWINS

¹ Seton Hill College, Greensburg, Pennsylvania, and the Marine Biological Laboratory, Woods Hole, Massachusetts

1. Young adult zooids of Amaroecium constellatum were divided into branchial and abdominal halves.

2. Two branchial halves and one abdominal half were inserted into the tunic of a two-week-old zooid from which the occupant had been evicted.

3. The three halves were mildly macerated in order to bring their injured surfaces into contact.

4. The epidermal mantle of the three half zooids, by the spreading action of its cells, enclosed the triple members in a common epidermal mantle.

5. The organ-parts in each contributing half ressembled their fragments into complete organs.

6. Union of organ-parts was effected only between tissues of matching histogenetic character.

7. When the dissociated organs re-established their integrity, the organs of each half united with their homologous members in each other half.

8. The re-establishment of organs into systems followed the system of axial gradients that characterize these tunicate zooids.

9. Within five days, three halves of three zooids reaggregated their constituent parts into functioning Siamese twins demonstrating various patterns of recombination.