ABSTRACT
Anucleolate Xenopus mutants have survived in parabiosis with normal individuals for four times their usual life-span. All tissues survive at least twice as long in parabiosis as they do in control anucleolate larvae. Lethality is thus concluded to be a secondary effect of the mutation, probably resulting from a defective blood-circulation.
Several anucleolate tissues are lost despite parabiosis, but not in a manner suggesting a cell-lethal action. The mutation is better described as cell-sub vital.
The anucleolate syndrome, of neural pycnosis and general retardation of differentiation and growth, is maintained in parabiosis. These symptoms may be direct results of the mutation in each cell. Some further cellular differentiation’ and growth in parabiosis show that the mutation does not completely arrest development.
The anucleolate syndrome is found to be consistent with the theory that the nucleolus regulates some basic process of cellular metabolism.