PRIMITIVE TYPES OF INTELLIGENCE 183 
aquarium quickly rushed, in obedience to its proclivity to 
shun the light, into the dark corner where it got into difficul- 
ties with the devil fish. Bethe now interfered and freed the 
crab from its captor and put it back in the aquarium. Back 
the crab went again into the arms of the enemy. Five 
successive times it repeated the performance (and another 
individual did the same six times) without learning to avoid 
the retreat of the devil fish. 
In another experiment a piece of meat was placed in an 
aquarium containing some hungry crabs, and the hand of 
the experimenter was held over the meat. Whenever a 
crab seized the food the creature was maltreated and driven 
away; it was thought that if the crab were capable of learning 
it would come to associate the sight of the experimenter’s 
hand with the painful experience following the seizure of 
the meat and keep at a distance. After several such ex- 
periences it went after the meat as at first, and Bethe 
concluded that the creatures were nothing but “reflex 
machines,” without a glimmer of intelligence. 
These few experiments by which the intelligence of the 
crab is summarily disposed of, form an almost amusing 
contrast to the long, detailed and exhaustive work on the 
anatomy and physiology of the nervous system. The 
experiments are obviously inadequate, not only because 
they are much too few in number, but because they do not 
afford the best opportunities for bringing out whatever 
power of forming associations a crab may possess. In the 
first experiment, granting that the crabs were not more 
afraid of Bethe than of the devil fish, as they had apparently 
as much reason for being, it would have been necessary for 
the crab to inhibit a strong instinct before it could manifest 
any tendency it may have acquired to avoid the dark corner 
with its sinister occupant. A crab when afraid makes for a 
