MORPHOLOGY OF BRAIN AND SENSE ORGANS OF LIMULUS. 29 



association either as a tasting or a smelling organ with the 

 process of eating. But it is very difficult to explain why 

 these movements are not produced by direct stimulation with 

 food. On the other hand^ the extraordinary hugging and 

 grasping movements of the second pair of legs in the males 

 clearly show that they are in some way functionally asso- 

 eiated with the olfactory organs. Now it is well known 

 that these legs in the male are specially modified for grasp- 

 ing the female during copulation ; and^ as I have shown 

 that they are the only legs not involved in the reflex 

 chewing movements caused by stimulating the mandi- 

 bles, I can conceive no other explanation for these facts than 

 that the olfactory organ is used by the males in detect- 

 ing the females. This is, moreover, a function for which 

 its position is well suited. That an organ for this purpose 

 must be present seems certain, for the males during the breed- 

 ing season hunt out the females and attach themselves to them 

 with great precision. It is hardly probable that this could be 

 done by means of touch or vision. While I can find no im- 

 portant difference between the structure of the olfactory organ 

 in the adult males and females, in the young I find that the 

 median olfactory nerve has an enormous ganglionic enlarge- 

 ment in some individuals and a much smaller one in others, 

 and I suspect that the former are males and the latter are 

 females. Again, when sound males and females are put in 

 the same aquaria, the males usually attach themselves to the 

 abdomen of the females, but I have never seen a male whose 

 olfactory organ has been cut out (and I have had, at different 

 times, half a dozen such specimens) attached to a female. This 

 experiment might be conclusive if it were performed on a 

 larger scale. Unfortunately I did not have sufficient material 

 to do this. 



I have tried several times to arouse movements of the second 

 pair of legs in the male by rubbing the olfactory organ with 

 fresh ova, and with the secretions of the oviduct, but without 

 success. Renewed experiments are necessary here, for I have 

 not given this aspect of the question the attention it deserves. 



