Abstract
Conclusions
1. The “Creeper”-factor, both in homozygous and in heterozygous condition, acts locally in the limb-forming areas at least from the stage of the first visible appearance of the limb buds on. 2. In particular, the possibility that the Cp-factor acts indirectly by causing a deficiency of any substance contained in the blood circulation (nutritive, hormones, Ca, etc.) is ruled out. The transplantations were made shortly after onset of circulation. 3. Wing and leg primordia of early lethal CpCp-embryos differentiate into “phocomelic” appendages if transplanted to a normal host. This confirms Landauer's 2 findings that “phocomelus” is the manifestation, in the appendages, of the Cp-factor in homozygous condition. 4. The fact that CpCp-limb primordia survive the critical stage of lethality if incorporated in a normal host suggests that the cause of lethality resides not in the limb-forming area but in another structure outside of it.
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