MORPHOLOGY OF BRAIN AND SENSE ORGANS OP LIMULUS. 27 



attempts to stimulate the olfactory organ with various kinds of 

 food, with acids and ammonia, I have never succeeded in pro- 

 ducing any characteristic reflex movements in that way. Even 

 drops of strong hydrochloric acid or ammonia seem to have no 

 more eflFect than when applied to other parts of the body ; they 

 cause a slight start, nothing more. 



In order to remove all doubt as to its glandular nature, I 

 have excised the olfactory organ, wiped its outer surface dry, 

 and then stimulated with electricity the attached nerves, but 

 have never seen any traces of a secretion, such as might be 

 formed provided it were a gland. 



Although these negative results are a little surprising, they 

 do not render the sensory nature of the olfactory organ any 

 less probable ; for we cannot expect every sense organ to give 

 on stimulation such beautifully '' diagrammatic reflexes " as 

 those on the mandibles. However, I finally discovered that 

 electrical stimulation of the olfactory region produced at once 

 very remarkable leg movements, such as are never seen under 

 any other circumstances.^ The experiment is not always suc- 

 cessful, but when it is, the moment the electrodes are 

 applied to the olfactory organs of the male, rapid 

 chewing movements of the mandibles are produced, 

 accompanied by vigorous snapping of the chelicerse, 

 which may finally become rigid and stretched out 

 backward at full length. At the same time the 

 second pair of legs, which during all our preceding 

 experiments on the gustatory organs have remained 

 motionless, are now quickly and repeatedly flexed, 

 as though trying to hug or grasp some object and 

 force it toward the mouth; all the other legs remain 

 motionless. Stimulation of the region about the olfactory organ, 

 or along the median line between the olfactory organ and the 

 brain, or above the brain, may produce the same eflPect. It is a 

 remarkable fact, for which I can give no explanation, that one 

 does not always get the same results on stimulating the 



* I subsequently observed similar movements of tlie second pair of ap- 

 pendages when the olfactory organ of a male was excibed. 



