Abstract
The study of mutual interactions between developing fish and amphibian tissue was tested by implanting parts of fish blastulæ into the blastocœle of developing amphibians. This method applies also to the study of the capacity for differentiation of isolated embryonic cells of the teleostean. Halves of blastulæ of the eggs of Danio rerio (the Zebra fish), isolated from their yolk an hour before the commencement of the visible processes of gastrulation, were implanted into the blastocœle of Triturus torosus eggs. The hosts were fixed after 10 days of development.
The developing fish and amphibian cells are mutually compatible during gastrulation and the stages immediately following. Thus developing tissue of young embryos from different classes of vertebrates at first possess considerable tolerance, even though a marked tissue specificity characterizes the adults. In the present series of experiments, the implanted fish material developed wherever located: in the center of the yolk, between yolk and epidermis, or surrounded by amphibian mesenchyme. The fish mesenchyme mingled with that of the amphibian to form a composite tissue. The tremendous difference in size between the fish and the amphibian cells is an aid in distinguishing the source of the tissue.
The amphibian epidermis is always locally thickened adjacent to an implant. In some cases there were extensive epidermal proliferations, sometimes richly provided with chromatophores though formed from normally unpigmented belly ectoderm. One of these bore an extension simulating in structure an amphibian dorsal fin.
In contrast to these cases of doubtful induction, another embryo shows a true one. Fish notochord induced the formation of amphibian nervous tissue from amphibian ventral ectoderm. It is clear that the processes which normally take place in the organizer-region of the fish can stimulate amphibian cells to differentiate specifically.
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