Experiments on the Early Development of the Amphibian Embryo etc. 631 



Comparative Influence of Solutions upon Eggs and Embryos in 

 Different Stages of Development. 



It remains for us to determine, if possible, the relation of the 

 influence of these solutions to the rapidity of development on the 

 one hand, and on the other to the period of development at which 

 the embryos are first subjected to that influence. 



In order to ascertain these points the following experiments 

 were instituted. 



Care was taken to determine exactly the condition of the egg 

 or embryo before it was placed in the solution. For this purpose 

 in all doubtful cases samples were preserved, and the final decision 

 was made only after sectioning*. 



The experiments include all three species of amphibians, and 

 many different stages in the development of each. So far as these 

 species are concerned, therefore, the conclusions are trustworthy. 



Experiment 1. A single bunch of Rana eggs was obtained 

 on March 23^*^ which, when examined, proved to have the third 

 furrow just developed. 



One hundred of these were cut out of the egg membranes and 

 placed free in a 0.6% salt solution, with as many more left within 

 the membranes. The remainder of the eggs were allowed to develop 

 normally for 24 hours, when two hundred more were placed in the 

 salt solution under the same conditions. The rest again developed 

 normally for 24 hours and were then all put in the salt solution. 

 All eggs placed in the solution free from the membranes developed 

 to the closing of the neural folds with a loss of less than 10%, 

 but then, or within 24 hours after, they all died. Those which had 

 been left for 48 hours had nearly reached this stage before being 

 placed in the solution, and so lived but a few hours longer. The 

 first lot stopped segmenting altogether for a short time when placed 

 in the solution, and then began again. The second lot seemed to 

 stop for a longer period than the first, and the third lot longer than 

 the second. The actual time was not taken, so that only a rough 

 comparison could be made, but enough was observed to suggest 

 that the effect of the solution was increased with the age of the 

 embryo. 



This suggestion was the only outcome of the experiments, for 

 these embryos all died on or before March 30*^\ 



