LIFE HISTORY OF DESMOGNATHUS FUSCA. 



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each side, the most anterior being the extensive one anterior to 

 the first gill arch and beneath the gular fold. Previous to 

 metamorphosis the gular fold becomes noticeably shortened, 

 keeping pace with the shortening of the cartilaginous arches. 



a 



FIG. 25. (a) A dorsal view of the hyo-branchial apparatus of an aquatic larva 

 collected in mid-winter, showing the typical larval structure. The shading indicates 

 the regions which will atrophy at metamorphosis. The dotted lines indicate the 

 regions where the accessory horns (hn) will develop at the time of metamorphosis. 

 Bbn and bbn, first and second basibranchials; cbr\ and cbn, the first and second 

 ceratobranchials; ch, ceratohyal; ebr i, 2, 3, and 4, the four epibranchials. Drawn 

 with Abbe camera from a preparation stained in situ with methylene blue, and 

 cleared with clove oil. X 40. 



(6) A dorsal view of the hyo-branchial apparatus of an adult Desmognalhus fusca. 

 Designations as in (a). Note the persistence and ossification of the posterior 

 end of the second basibranchial, forming the os thereoideum of Wiedersheim ('77). 

 Drawn with Abbe camera from a dissection. X 6. 



