Experiments on the Early Development of the Amphibian Embryo etc. 647 



Explanation of Plate X and XI. 



All the figures were drawn with a Camera lucida. 



Figs. 1 to 9 are serial surface views of Amblystoma eggs and embryos 

 developed in 0.6% salt solution: the eggs being unsegmented when placed 

 in the solution. 



Fig. 1. Surface view of inferior hemisphere of a living egg showing first be- 

 ginning of the blastopore invagination after being in the solution 72 hours. 

 Magnified 36 diams. 



Fig. 2. Surface view of inferior hemisphere of a living egg which had remained 



47 hrs. in a 0.4% solution. Magnified 36 diams. 

 Fig. 3. Surface view, posterior, of living egg 103 hrs. in 0.6% salt solution. 



Magnified 36 diams. 



Fig. 4. Surface view of living embryo (dorsal) 123 hrs. in the solution. Showing 



formation of the neural folds and groove. Magnified 36 diams. 

 Fig. 5. Surface view of freshly killed embryo just at the closing of the neural 



folds, 140 hrs. in the solution. Magnified 36 diams. 

 Fig. 6. Surface view (lateral) of freshly killed embryo 11 days in the solution. 



Showing posterior elongation of dorsal lip of blastopore and large free 



yolk plug. Magnified 36 diams. 

 Fig. 7. Surface view (lateral) of preserved embryo 17 days in the solution, 



showing external gills and balancer. The free yolk in this embryo was 



extraordinarily large. Magnificed 24 diams. 

 Fig. 8. Surface view (lateral) of preserved embryo 20 days in the solution, 



showing closure of the blastopore, and almost entire disappearance of all 



traces of the free yolk plug. This embryo is essentially normal in all its 



external features. 



Fig. 9. Surface view, enlarged, of posterior end of an embryo 103 hrs. in a 

 0.4% solution, showing temporary anus and comparative size of yolk and 

 pigment cells. Magnified 52 diams. 



Fig. 10. Surface view (lateral) of an embryo showing abnormal separation of 

 the posterior portion of the dorsal organ from the yolk plug. 



Figs. 11 — 14 are sections of the same series showing formation and gradual 

 closure of the blastopore. All from 0.6% solution. 



Fig. 11. Median section of blastula, showing segmentation cavity and the be- 

 ginning of gastrulation. 



Fig. 12. Median vertical section of posterior end of embryo showing pigment 

 layer over surface of the yolk, and thickened dorsal lip of the blastopore 

 120 hrs. Magnified 50 diams. 



Fig. 13. Similar section 40 hrs. later in development showing partial witn- 

 drawal of the yolk plug and downward growth of the dorsal lip of the 

 blastopore. 



Fig. 14. Similar section 32 hrs. later in development showing complete with- 

 drawal of yolk plug and formation of permanent anus. 

 Figs. 15 and 16 are outline sketches of normal Amblystoma embryos, 



showing currents generated by the cilia. Fig. 15 just after the closing of the 



neural folds and Fig. 16 12 hrs. later. 



