THE METAMORPHOSIS or LARVAE 439 



spinal cord or even after the removal of a piece. 1 In this 

 case also morphogenetic processes are independent of the 

 central nervous system. 



This objection may also be raised, however, that Tornier 

 has assumed in the development of the larvae a formative 

 influence of the central nervous system only upon the sexual 

 cells, and not upon the body cells. This objection must be 

 granted, but it must also be remembered, on the other side, 

 that it is risky to assume such a formative effect of the 

 central nervous system where we have no means to ascertain 

 the facts, while we can show that such an influence does not 

 exist where the facts can be studied experimentally. That a 

 set of muscles cannot functionate without the corresponding 

 segments of the central nervous system is certain, but it is 

 equally certain from the experiments of Goltz and Ewald 

 that the blood-vessels behave differently. It is, at present, 

 to say the least, just as probable that the central nervous 

 system does not influence the sexual cells as that the opposite 

 assumption of Tornier is true. 



If it be assumed, on the other hand, that the formation of 

 organs, or that morphogenetic processes in general, are 

 determined through chemical substances which are formed 

 in the metabolism of the animal and circulate through the 

 animal, it is clear that, in spite of the division of the central 

 nervous system, metamorphosis must occur simultaneously in 

 both portions of the animal anterior and posterior to the cut. 

 This assumption also does away with the necessity of formu- 

 lating independent laws for the development of organisms 

 with and without the central nervous system. In various 

 papers I have pointed out that the facts of morphogenesis can 

 be explained on a chemical basis, as Sachs has first suggested. 



I will not here discuss the question of the inheritance of 

 acquired characteristics. 



1 GrOLTZ UND EWALD, Pflugers Archiv, Vol.LXIII. 



