THE SPEED OF MIGRATION OF SALMON 
585 
Recently Edinger^ has called attention to the fact that the low 
form of the brain of the lower vertebrates must be taken into 
consideration in judging the reactions of such animals to stimuli. 
The salmon, for example, should be considered in view of its bio- 
logical position in the animal series. Its brain is very simple 
in type. The cerebral lobes are small and the cortical structures 
of relatively shght complexity. If the salmon possesses any 
association tracts they are very simple. Such a low form of 
brain cannot execute very complex reactions. There is not the 
necessary anatomical machinery. The brain and spinal cord are 
capable of carrying on only the usual reflexes of muscular move- 
ment, circulation, respiration, etc. It is to be assumed that the 
injur}' to the skin, as for example punching the hole through the 
tail for the marking button, leads to little more than the reflex of 
muscular movements. As a matter of fact direct observation 
shows that these muscular responses are relatively slight, and 
include little more than the motions of swimming. There is 
in addition a transient inhibition of the respirator}' movements. 
Judging from the results of other experiments, one may assume 
that there will be some slight disturbance in the coordination of 
the circulatory apparatus. These more or less complicated 
reflexes disappear within a few minutes at most. 
Those conditions which lead to the migration of salmon are 
the chief directive stimuli at the migration time. They supercede 
all other stimuli. In comparison with them the effects of tran- 
sient stimuli, such as cutaneous lesions, etc., are insignificant. 
Large numbers of fish taken in the upper waters of the Columbia 
River are injured in one way or another. Some of them have 
received lacerations man}- fold greater than that inflicted upon 
the fish for the purposes of marking. Yet these fish are forging 
ahead toward the spawning grounds with apparently no digres- 
sion. 
* L. Edinger: Ueber das Horen der Fische und anderer niederer Vertebraten; 
Zentralb. f. Physiol., 22, 1, 1908. 
