An editable svg file of this figure can be downloaded at The donor tissue primarily forms the notochord. Most of this second body is made of host tissue. Transplantation of the dorsal lip of the blastopore from a donor to a host of a closely related species gave a second body axis. Figure 6: The Spemann-Mangold experiment. 2) The notochord patterns the tissue around it to make the primary body axis 15. This meant two important things: 1) The dorsal lip of the blastopore develops into the notochord. They found that only a tiny portion of the twinned tadpole tissue was unpigmented - the notochord (plus some additional cells here and there - the technique was not completely perfect). In this way she was able to see which tadpole tissues came from the donor (the unpigmented newt) and which from the host (the pigmented newt). Mangold took the blastopore lip from an unpigmented newt species and transplanted under the ventral ectoderm of an early gastrula pigmented newt from the same genus. Soon Spemann revised his hypothesis, largely based on careful observation of gastrulating embryos and on the cross-species transplantation work by Mangold. When he transplanted the dorsal lip from one newt to another, he got conjoined twin newts - suggesting that some signal from the dorsal lip was indeed patterning the main body axis 12,13. Spemann thought he had support for this hypothesis when he did transplantation experiments in newts. Without this signal, cells wouldn't differentiate. One possibility was that a morphogenic signal emanated from the dorsal lip that caused cellular differentiation in a time gradient, such that the closest cells to the dorsal lip differentiate first. He knew it was important because if he sliced an embryo in two, the half that got the dorsal blastopore lip developed into an tadpole, while the other half developed into a "belly piece." He also knew that if he carefully divided the embryo down the middle of the dorsal lip of the blastopore, both halves would develop into a tadpole. Spemann had wondered for years what exactly the dorsal lip of the blastopore did. Hans Spemann and his graduate student Hilde Mangold perfected a technique to do cross species transplantations of the dorsal blastopore lip to new locations in the host's body.
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