PLATE 16 



EXPLANATION OF FIGURES 



Cross-sections of metamorphic stage IV. X28 



44 Level corresponding to metamorphic stage III, figure 38, showing the 

 infolding of the pharyngeal mucous mmbrane to form the tongue stalk, the fur- 

 ther flattening out of the basibranchial, and ceratohyals, and the complete loss 

 of the M. ceratohyoideus externus anteriorly. 



45 Level corresponding to adult, figure 24, showing posterior limit of forma- 

 tion of tongue stalk. 



46 Level corresponding to metamorphic stage III, figure 40, showing nearly 

 complete degeneration of M. ceratohyoideus externus. 



47 Level corresponding to metamorphic stage III, figure 42, showing the spiral 

 muscle beginning to fill out to its adult proportions, and the M. thoracicohyoideus 

 nearly transformed into Mm. abdominohyoideus and sternohyoideus. 



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