INEZ WHIPPLE WILDER. 



PLATE IV. 



FIG. 17. Vertical section through the skin of the dorsal surface of a 13 mm. 

 embryo of 30 days'- development, showing the characteristic two layers of epidermal 

 cells. 



FIG. 1 8. Vertical section through the skin of the lateral surface of a 13 mm. 

 embryo. 



FIG. 19. Vertical section through the skin of the dorsal surface of a newly 

 hatched terrestrial larva, stage A. Note the presence of a corium of dense con- 

 nective tissue beneath the two layers of epidermal cells, the absence of mitosis in 

 the epidermis, and the development of an external cuticle from the outer borders 

 of the outer layer of cells. 



FIG. 20. Vertical section through one of the integumental sense organs in the 

 region of the gular fold, terrestrial larva, stage A. 



FIG. 21. Section parallel with the external surface, through the outer layer of 

 epidermal cells, dorso-lateral surface, terrestrial larva, stage A. 



FIG. 22. Similar section through the inner layer of epidermal cells, dorso-lateral 

 surface, terrestrial larva, stage A. 



FIG. 23. Vertical section through the skin of the dorso-lateral surface of an 

 aquatic larva collected in September. Note the presence of numerous Leydig 

 cells in the deeper layer. 



FIG. 24. Section parallel with the external surface, through the outer layer of 

 epidermal cells from a lateral, unpigmented region of the body of an aquatic larva 

 collected in September. 



FIG. 25. Similar section through the inner layer of epidermal cells, lateral 

 region, of an aquatic larva collected in September. 



