204 COMPARATIVE PHYSIOLOGY OF THE BRAIN 



to this theory, every change that takes place in the 

 body is said to be accompanied by a corresponding 

 change in the central nervous system. The changes 

 in the central nervous system are then said to bring 

 about a corresponding change in the egg. Thus, ac- 

 cording to this theory, just as close a relation must 

 exist between the central nervous system and the 

 morphogenetic processes as between the central nerv- 

 ous system and the motor and sensory functions. 

 It can readily be shown, however, that this assumption 

 of Tornier goes much too far. When the larva of 

 Amblystoma transforms itself into a sexually mature 

 animal, it loses the gills which are located on the head 

 and the tail-fins that are on the tail. Both organs 

 disappear simultaneously. In a series of Amblystoma 

 larvae I severed the spinal cord in the vicinity of the 

 shoulder-girdle. The parts of the animal before and 

 behind the place of division are, as regards motor and 

 sensory functions, like two separate animals. If the 

 morphogenetic processes were as closely related to 

 the central nervous system as the sensory and motor 

 functions - - as Tornier's theory demands - - we should 

 have expected that the gills and tail-fins would no 

 longer be absorbed simultaneously, but at different 

 times, just as in two different animals. Without ex- 

 ception, in these animals with severed spinal cord the 

 absorption of the head- and tail-organs occurred simul- 

 taneously (i). In some of the animals operated upon, 

 the change took place in a few days after the division, 

 in others a longer interval elapsed. There can thus 



