OF THE HEAD l.N THE BATRACHIA URODELA. 



Ill 



The next younger stage (text-fig. 43), again, shows a large 

 ventral piece of the first myotome. At a still younger stage 



cfr. 



Text-fig. 43. 

 f.. 3s. mtj^2 



spg. 



Left side view of a reconstruction of tlie antei'ior region. 

 The visceral arches are not completed. 



(text-fig. 44), the trabeculse have not appeared and the visceral 

 arches are represented by mere rods of procartilage. 



mi 



Text-fig. 44. 

 gv. rnr'^^ as. f. 



mt' hrls. "^3 



Right side view of a reconstruction of the anterior end of a larva in which the 

 raesoblastic skeleton is represented only by procartilaginous rod-like visceral 

 arches. 



We now come to embryos without true mesoblastic skeleton. 

 These earlier stages are most important in determining the number 

 of postauditory segments. Text-figs. 45 and 46 are reconstructed 

 from an embryo 5 mm. in length ; they both are views from 

 above, but text-fig. 46 reaches farther down, so as to include 

 the alinieutary canal nnd optic vesicles. Myotonies 4 and 5 are 



