544 METAMORPHOSIS IN AMPHIBIANS 



3. The development of the adult skin coloration and of the legs 

 may take place either before or after metamorphosis. Iodine cannot 

 enforce either of these phenomena. 



4. The same is true of the development of the sex organs. 



5. Development of the tongue and palatal teeth can be checked 

 even in animals in which metamorphosis takes place. 



6. Consequently development of the skin coloration, as well as 

 development of the legs, sex organs, tongue, and palatal teeth are all 

 caused by substances not identical with the substances causing meta- 

 morphosis and, since they are also all independent of each other in 

 their development, it is probable that special chemical mechanisms 

 exist for the develqpment of each one of these six groups of organs. 



7. This assumption is also supported by the fact that the order of 

 - development in several of these organ pairs can be changed by a 



difference in temperature, which would indicate that the develop- 

 ment of each of these groups of organs is caused by chemical reac- 

 tions with different temperature coefficients. 



8. That the germ cells can develop in amphibians either before or 

 after metamorphosis does not mean that the germ plasma is opposed 

 as a unit to the somatic plasma, since other organs which are believed 

 to be part of the somatic plasma behave in this respect like the germ 

 cells. 



9. The noteworthy feature of the amphibian metamorphosis is that 

 instead of being controlled and kept in harmony by the organic indi- 

 vidual the development of at least six groups of organs is controlled 

 separately by the action of probably six different chemical mechan- 

 isms, each of which can be stopped or enforced independently either 

 by directly supplying the substances required or by causing an 

 increased formation within the body by suitable temperatures. 



