Abstract
A series of experiments were performed dealing with the effect of varying the osmotic pressure of the solution, on the disintegrative action of potassium cyanide, on the early embryos of Amblystoma punctatum. The experiment was carried on during the Spring of 1926. Owing to the unusually short season, the work is incomplete in many respects, and further experiments are planned for future seasons. However, certain very definite results have been obtained, which appear to have an important bearing on the general problem of susceptibility and susceptibility gradients.
In each experiment a batch of embryos from a single female was selected and dissected free from the jelly capsules. This was necessary because preliminary experiments showed that the capsules afford some protection against KNC. The embryos were allowed to remain for a number of hours in cold running tap water, during which time any that had been injured died. To freshly made solutions of commercial cane sugar, Ringer's solution, urea (made up in both distilled and tap water), and to distilled and tap water was added sufficient KNC to make the desired concentration. The range of concentrations employed was: Sugar, 0.03 molal to 0.6 molal; Ringer's solution, 1/10th to double the usual concentration; urea, 0.03 molal to 0.6 molal; KNC M/250 to M/125. As regards the osmotic pressure of the solutions, a crude cyroscopic method served to demonstrate that solutions of sugar of the order of 0.15 molal and Ringer's solution diluted one-half are both hypertonic for the Amblystoma embryo in the stages employed. Saturation with oxygen was assured by shaking the solutions with air: The embryos were then placed in 250 cc. Stender dishes in tap water, and the water replaced by 250 cc. of the desired solutions.
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