HOMOPLASTIC GRAFTING IN STENTOR COERULEUS

¹ Arnold Biological Laboratory, Brown University, Providence, R. I.

1. A technique is described which permits oriented grafting of two or more whole Stentors or fragments.

2. Fusion complexes in S. coeruleus are invariably labile. If the surface organelles of the component units are too severely disrupted, the complex disintegrates. In viable homopolar systems, all but one of the units dedifferentiate, and a single enlarged individual is formed. In heteropolar systems, the units maintain their individuality and finally constrict apart, in a process strikingly reminiscent of fissional constriction. Random multiple complexes first acquire one of three characteristic patterns of organization, and then reorganize into single organisms by either or both of the methods mentioned.

3. In a homopolar parabiotic doublet, the unit which later dedifferentiates is always the smaller component. It cannot regenerate excised parts, even before its individuality is suppressed. On the other hand, if the oral organelles of the larger component are excised, they do not regenerate, and the smaller unit becomes dominant. In heteropolar complexes, each unit can regenerate excised parts, regardless of its initial relative volume.

4. Macronuclei are found to be cross-active, nodes of one unit maintaining normal function and the capacity of differentiation in an enucleated unit. However, the particular status of dominance of a unit is abolished by enucleation.

5. Questions raised by the experiments are shown to be reducible to problems of kinetal and kinetosomal function. As far as is possible, therefore, the results are interpreted in terms of activities of kineties and kinetosomes, ectoplasmic organelies known to be decisively involved in processes of ciliate morphogenesis.