234 HUBERT DANA (tOODALE 



Several observers, viz., Lwoff ('94), Eycleshj^mer ('95) and 

 others, obtained very divergent results within their own experi- 

 ments. An exovate made in the dorsal lip of the blastopore 

 when it first appeared was sometimes found in the head and at 

 other times in the tail. Miss King's ('02) results explain these 

 discrepancies.^' 



I think, then, it is reasonable to suppose that the advance of 

 the lip is variable, being about 75° for the frog and less in other 

 forms. In Hypogeophis, according to Brauer, its advance is 

 very slight. 



The effect of cold and of salt solutions 



Before taking up the question of concrescence, I wish to record 

 a few experiments which have considerable bearing on this ques- 

 tion and the question of spina bifida embryos. 



In the first experiments, the effects of cold were tried on the 

 eggs. This has additional interest, since the eggs of Spelerpes 

 are frequently laid in extremely cold spring water. 



Freshly laid eggs were placed in an ice chest with some frog's 

 eggs for comparison. The temperature of the water in which 

 the eggs lay was about 5° C. Beyond a slowing of development 

 — the neural folds appeared twenty-three days after the eggs were 

 placed in the chest — no other effect was apparent. Normal 

 embryos resulted. The frog's eggs, on the other hand, almost 

 all developed abnormally producing various forms of spina 

 bifida. 



The effect of salt solutions was also tried. Eggs in early 

 cleavage stages were placed in solutions of NaCl, KCl and LiCl. 

 About 0.5 per cent solutions gave best results. In more concen- 

 trated solutions, the eggs died and in weaker ones, no effect was 

 visible. A complete study of these embryos is yet to be made. 

 The most striking feature of the results is the entire absence of 

 ordinary spina bifida embryos. The embryos are somewhat 

 shorter than normal. The posterior ends of the neural folds 



'5 Sev page 236. 



