Abstract
The perfect union of the anterior and posterior halves of the embryos of 2 species of anurans 1 and the metamorphosis 2 of such a combination into a perfect adult was shown to be possible by Harrison 30 years ago. Up to the present day the opportunities which this operation makes possible have never been realized. The intention of the present report is to demonstrate that such combinations can be produced in large enough numbers to enable the experimental embryologist and geneticist to carry out a variety of new studies.
The frog embryos employed were Rana palustris and Rana sylvatica. Those of the salamander used were Amblystoma tigrinum and Amblystoma punctatum. The stages at which the operation was done were in the early tail-bud period of development.
The species conbinations in their respective classes are, at the tail-bud stages, about the same in size. Similar stages in development were selected and placed in slightly diluted Ringer's solution in an operating dish, the floor of which was covered by a thick film of white beeswax. The embryo was oriented under the microscope, dorsal side up, between fine forceps so that iridectomy scissors could, with one stroke, cut the embryo transversely at the level of the seventh to eighth somites. It is quite possible to cut at other levels as well in making successful combinations.
The anterior half of one species and the posterior half of the other were then placed in a depression in the wax which was about the size of an intact embryo. The cut surfaces of the reciprocal halves were brought together in the concavity of the wax as soon after the operation as possible.
Get full access to this article
View all access options for this article.