618 



Chas, B. Wilson 



which originally led to the undertaking of the experiments, and for 

 much subsequent advice and assistance. 



To Prof. John M. Tyler and Libarian Wm. I. Fletcher of Am- 

 herst College sincere thanks are due for the free use of the Reference 

 Libary, an invaluable aid in any investigation, and to Prof. Harris 

 H. Wilder for a similar privilege at Smith College. 



Experiments with 0.6% salt solution. 



Two bunches of Amblystoma Eggs were obtained on March 7*^. 

 In one of these the eggs were unsegmented, in the other they were 

 in the blastula stage. 



Both bunches were used to verify experiments undertaken upon 

 the same species at the suggestion of Dr. Andrews in the spring of 

 1895. An effort was then made to ascertain whether the results 

 obtained by 0. Hertwig (23) upon R. esculenta, and R. fusca would 

 also hold true for Amblystoma and R. temporaria. 



In Hert wig's experiments » thoroughly healthy « eggs were first 

 fertilized and allowed to lie for an hour and a half. They were 

 then put into six different solutions of common salt, of strengths 

 varying from 0.5 to 1 7o- Hert wig found that the 0.6% solution 

 yielded the most interesting results and accordingly that strength was 

 used in the present instance. But he was unable to carry any 

 embryos beyond the sixth day through lack of material. 



In attempting to verify his experiments it was determined to 

 rear some of the embryos at least to the formation of the internal 

 gills, or the true tadpole stage. The attempt proved successful and 

 fully developed tadpoles were obtained, while Hertwig's results 

 were verified in nearly every essential particular. There were several 

 important differences in detail, however, and since the present in- 

 vestigations were carried so much further than his they furnish much 

 that is new and interesting. 



General Results. 

 All the eggs were removed from the gelatine, and half of each 

 bunch were freed entirely from the surrounding membranes. Those 

 in the blastula stage were put into a 0.4% solution, while the un- 

 segmented eggs were placed in a 0.6% solution. The eggs from 

 which the membranes were removed developed to the closing of the 

 neural folds and then all died. Of the remainder, those in the 0.6 % 



