636 



Chas. B. Wilson 



at different stages of development, and in this instance eggs of the 

 same species, placed simultaneously in the same solution under 

 exactly similar conditions, and yet yielding very different results. 

 They vrere necessarily taken from different bunches, but in the one 

 case (Experiment 6) we find the Amblystomas all alive after 17 

 days development, and nearly all presenting a perfectly normal 

 appearance (fig. 8). In the other case (Experiment 7) we find a much 

 larger percent with their yolk plugs still protruding at the formation 

 of the external gills (fig. 7), while nearly half (45%) of them died 

 before reaching that stage. Considerable difference could also be 

 detected in the early development of the two bunches in the present 

 experiment. 



Experiment 8. Amblystoma eggs with the blastopore just 

 developed were placed in Einger solution March 27*^. In these very 

 large yolk plugs were left protruding, even at the end of 16 days 

 development, at which time also nearly all (90%) of them were dead. 



By comparing these eggs with those in Experiment 6 several 

 interesting facts appear. 



These eggs had developed normally until the blastopore was 

 fully formed and its borders had begun to contract. But on being 

 placed in Einger solution the action, begun and carried so far 

 forward, was not completed, and the yolk plug remained very nearly 

 of its original size. On the contrary the 4 cell eggs, in which even 

 segmentation was scarcely commenced, formed a blastopore at the 

 proper time, and most of them completely closed it. 



Again the two lots of eggs were placed in the solution within 

 an hour of each other, but at the end of ten days the 4 cell eggs 

 were as far developed as the others. At the end of 16 days they 

 were much farther developed, notwithstanding the fact that the eggs 

 of the present experiment had so much the start of them. The 

 difference between the 4 cell stage and gastrulation represents about 

 three days development, and yet this comparatively large handicap 

 was overcome within 10 days time. Evidently in this instance the 

 influence of the surrounding medium was greatly modified by diffe- 

 rences in the stage of development at which the egg was subjected 

 to it's action. 



Experiment 9. Chorophilus eggs, unsegmented, were placed 

 in Einger solution. These eggs did not seem to lie dormant at all, 

 but continued developing at once. The influence of the solution 

 upon their development, however, was very marked in other ways. 



