Xo. 638] INTERNAL SECRETIONS OF AMPHIBIANS 205 



iodine-free diet, does not in any way ivtai-.l lirowtli or 

 metamorphosis. 



There are several species of salamanders {Antoddr 

 luguhris, Autodax iecanus) whose young do not emerge 

 from the eggs before metamorphosis is completed. 

 Although the larvae of these species have no opportunity 

 to obtain iodine from outside, these cases do not i)r()ve, of 

 course, anything against the importance of iodine in the 

 amphibian metamorphosis; very likely tli.' fuus ot' 

 Aufoda.r contain enough iodine to permit nictanioriihosis 

 of the larva^ within the egg. 



Still another diffcnMH-e between annrans and salaman- 

 ders has ina(h' itself ap])arent in this woi'k. While in 

 tadpoles, of at least certain anuran species, the develop- 

 ment of the legs is, in some as yet unknown way, dis- 

 tinctly under the control of the thyroid, the leg-develop- 

 ment in salamanders is independent of the thyroid gland. 

 Both hind and fore limbs develop in a normal way after 

 thyroidectomy in salaniandei- h-if\a'. as shown by K. R. 

 and M. M. Hoskins (10). .More<.ver. the develojanent of 

 the legs is not accelerated if the larva- aiv kept in soln- 



eggs have been (h'i...sited. ConsiM |neii I ly , it is Very com- 

 mon to lind that the L-ir\a' inelanioi-)»hose in the iodo- 

 th\ rine solntion iiel'ore the h'gs are cotnph'tely developed. 



meat is eontn.lled ])y th'e thyroid fnnetion, sinee neither 

 the hind limbs, from a certain stage ..n. nnr the tore limbs 

 can develo]) in the absence of the thyroid (I*, bl. V.)). 

 Apparently the anuran thyroid gland begins to >eerete 

 already in' the larval period. In salamamh'rs the larva! 

 development seems to be highly imlependeiit of the thy- 

 roid function and it is (|uite prol)al)le that the salaTiumder 



moult. 1diis ran be demonstrated in the following way 

 ( If eys of (d<l larva' which, however, are still far 



enough from nu'tann)i-pliosis, are grafted on to young 



