EIGHT FIGURESThe studies reported here are the outgrowth of an unexpected observation incidental to experiments on the growth of eyes grafted embryonically from Triturus torosus to Amblystoma tigrinum (Twitty and Elliott, '34). It was noted that the Amblystoma hosts failed to become motile at the customary stage of development, and in fact remained completely paralyzed for a period of days during their subsequent differentiation. Two or 3 days before yolk resorption was complete the young larvae began to respond to stimulation and were soon entirely normal in their reactions. Except for their temporary immobility they had shown no signs of injury or developmental retardation, and were subsequently reared to metamorphosis. It was obvious from these results that embryos of the donor species must be the source of a toxin with specific physiological action, and this was soon confirmed by the injection of extracts (Twitty and Johnson, As the phenomenon with which we are dealing is essentially new and unexplored, a number of questions at once present themselves. I n the desire to provide as wide an orientation as possible, it has been necessary to make only an introductory attack on several of these questions, and to limit the more intensive studies in accordance with the time and '34).
Sci. Inst., (in press). 9 Unless otherwise stated, the National Bureau of Standards "Nuclear Data" compilation has been used for values of half-life and beta end-point energies.
Newts displaced after perfusion of the olfactory epithelium with formaldehyde failed to orient toward home, whereas control animals subjected to oral perfusion with formaldehyde oriented as readily as did untreated controls. Newts with surgically extirpated olfactory nerves failed to home unless their nerves had regenerated. These results strongly suggest a critical role for olfaction in homing behavior.
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