ABSTRACT
An analysis has been made of factors which can cause abnormal development of embryos derived from transplanted nuclei in Xenopus laevis. A distinction is made between innate and technical factors, and between those which affect donor nuclei and recipient eggs.
The innate developmental potentialities of endoderm donor nuclei do not appear to be limited, at least up to the early gastrula stage. Abnormalities known to be due to differentiated donor nuclei from later donor stages are described elsewhere. The technical treatment of donor nuclei can be carried out so as not to damage them, even if this is purposely made more severe than usual.
The innate capacity for development of recipient eggs was found to vary considerably from one spawning to another; this variation seems to be due to an inability of the eggs of any one frog to withstand technical treatment which may be shown to be harmless to the eggs of other frogs.
As the quality of recipient eggs can only be judged from results, experiments using Xenopus eggs should be accompanied by control transplantations, using donor nuclei the developmental capacity of which is already known. With these control transplantations for comparison, the technique is suitable for testing unknown developmental potentialities of different kinds of donor nuclei or recipient eggs.
