256 



BERTRAM G. SMITH. 



in the absence of experimental demonstration would hardly be 

 suspected. The neural folds, except their most anterior portion, 

 are formed from material lying originally at least 90 apart, or 

 one fourth the circumference of the egg. The forward movement 



FIGS. 32 TO 43. Each horizontal row of figures represents the history of an 

 individual egg of Cryptobranchus allehenicnsis. The dotted areas represent marks 

 made with Nile blue sulphate. Fig. 32, upper hemisphere of an egg in an early 

 neural fold stage, sketched immediately after marking. Fig. 33, upper hemisphere 

 of the same egg sketched a day later. Fig. 34, upper hemisphere of the same egg 

 sketched a day later than the preceding. Fig. 35, dorsal aspect of the same em- 

 bryo sketched a day later than the preceding. Fig. 36, upper hemisphere of an- 

 egg in an early neural fold stage, sketched immediately after marking. Fig. 37, 

 dorsal aspect of the same embryo sketched two days later. Fig. 38, dorsal aspect 

 of the same embryo sketched a day later than the preceding. Fig. 39, dorsal 

 aspect of the same embryo sketched a day later than the preceding. Fig. 40, 

 dorsal view of an embryo in the neural fold stage, sketched immediately after mark- 

 ing. Fig. 41, dorsal aspect of the same embryo, sketched a day later. Fig. 42, 

 dorsal aspect of the same embryo sketched a day later than the preceding. Fig. 

 43, lateral aspect of the same embryo sketched three days later than the preceding. 

 Four eggs were used for this experiment, with results so nearly identical that the 

 history of any one of these eggs might be represented by Figs. 40 to 43. 



