320 



INEZ WHIFFLE WILDER. 



taneously with the atrophy of the epibranchials there occurs an 

 atrophy of the whole of the second basibranchial except its 

 extreme posterior end, which persists and later ossifies to become 

 a little bifurcated structure designated by Wiedersheim ('77) 

 as the thyreoid bone (bbr 2, Fig. 25, b). With the atrophy of the 

 second basibranchial cartilage, which during larval life forms one 

 continuous chondrification with the first pair of ceratobranchials, 

 the latter become separated from each other and each articulated 



el))- 



FIG. 24. Horizontal section through the tongue and hyo-branchial apparatus 

 of a recently metamorphosed adult Desmognathus fusca (cf . with the drawing of the 

 whole apparatus shown in Fig. 25, b); bbr, basibranchial; cbr i and 2, first and 

 second ceratobranchials; ch. ceratohyal; hn, accessory horns for the support of the 

 adult tongue; Igl, lingual glands. Drawn with Abbe camera. X 32.5- 



with the first basibranchial. In the two or three final days 

 before metamorphosis the medial ends of the ceratohyals become 

 detached from the anterior ends of the first basibranchial (ch, 

 Fig. 22, b and d), while posterior to their former point of attach- 

 ment, a pair of cartilaginous processes grow out from the basi- 

 branchial to serve apparently as an additional support for the 

 tongue (hn, Figs. 22, d, 24, and 25). 



The final change which completes the atrophy of the gill 

 region is the closure of the gill slits of which there are four upon 



