PLATE 18 



EXPLANATION OF PIGTTRES 



•57. An albinous and a normal frog tadpole showing reciprocal sldn exchanges. 

 Taksn four hours after the skin exchange was effected. Age of specimens 70 days, 

 dated from the operative stage. X5, 



58. Enlargements of the skin exchanges and surrounding region of the specimens 

 shown in figure 57. 



148 



