THE METAMORPHOSIS OF LARVE 439 
spinal cord or even after the removal of a piece.’ 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 larve 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. 
1GoOLTz UND EWALD, Pfliigers Archiv, Vol. LXIII. 
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