PLATE 13 



EXPLANATION OF FIGURES 



Cross-sections of metamorphic stage II. X28 



33 Level corresponding to a section of larva between figures 7 and 8, showing 

 degeneration of anterior end of basibranchial and ceratohyals. 



34 Level corresponding to larva, figure 9, and metamorphic stage I, figure 30, 

 showing degeneration of basibranchial, ceratohyals, and M. ceratohyoideus 

 internus,' and anterior growth of Mm. abdominohyoideus and ceratohyoideus 

 internus. 



35 Level corresponding to larva, figure 10, showing degeneration of the plate 

 and of the median portion of M. thoracicohyoideus. 



36 Level corresponding to metamorphic stage I, showing further growth of 

 adult epibranchial, anlage of spiral muscle and degeneration of larval first 

 epibranchial. 



576 



