ENDOCRINE SYSTEM OF TYPHLOMOLGE RATHBUNI. 



307 



gill arch and median to this arch (Fig. 4). They extend in a 

 posterior direction ; the posterior end approaches closely the wall 

 of the lymph space, but does not come in contact with it. It is 



H7--M 



h.-- - 



FIG. 2. Location of median thy- 

 roid rudiment in Typhlomolge ~. B, 

 basibranchial ; //, hyoid; M, cavity 

 of mouth; T, thyroid rudiment. 



evident from this account that 

 the lateral rudiments of Typhlo- 

 molge occupy a location similar 

 to that of the main portions of 

 the thyroid in Ambystoma opa- 

 cum. They are, however, located 

 further anterior, as if they had 

 stopped migrating before attain- 

 ing the definite position. More- 

 over, the place where the anterior 

 cardinal vein passes the lymph 

 space is located considerably 

 more ventral ; therefore, the lat- 

 eral rudiments are nowhere in 

 contact with this vein. It is in- 

 deed impossible to see any vessels 

 supplying the thyroid rudiment; 



FIG. 3. Median thyroid rudi- 

 ment of Typhlomolge 7. X 340. 



-H. 



FIG. 4. Location of lateral thyroid 

 rudiment of Typhlomolge 7. I., first 

 gilljarch; II., second gill arch; G \, plate 

 of first gill; H, hyoid; L, lymph space; 

 M, cavity of mouth; O, operculum; T, 

 thyroid rudiment. 



