232 Dwellers of the Sea and Shore 



Moreover, while in the water, these animals never 

 seemed aware of my presence until I actually touched 

 them; whereupon the merest contactual disturbance 

 was enough often to cause them to strike out for the 

 deeper regions. This is what gave me a hint. 



I am going to put the cart in front of the horse, 

 somewhat, by saying at once that Limulus, after the 

 manner of creatures totally blind, makes its way by the 

 sense of feeling, and it determines its direction, or gen- 

 eral course, by the slope of the substratum. Let us 

 try an experiment. Taking for the purpose a full- 

 grown individual, we cover both its simple and com- 

 pound eyes with asphaltum or some other dense pig- 

 ment — an operation by no means distressing to the 

 animal since in this case the cornea is as hard and 

 feelingless as the carapace. Then placing the creature 

 on the hard-packed sand near the water's edge, we 

 watch Its movements. Does it grope about, uncer- 

 tainly, hesitatingly? Not at all. No matter in which 

 direction it is set — with its head pointed either toward 

 the sea or the land — it crawls unerringly toward the 

 water. In other words, it follows the declivity of the 

 sand, however slight this may be. But in this matter 

 it can be cieceived. If it be placed on the side of a 

 ridge that slopes away from water, it will amble to a 

 lower level, and not finding water it will force itself 

 into the sand. By removing the pigment and repeating 

 the process the result is the same. We may be sure 

 that it is by the same principle that the breeding ani- 

 mals are guided in their course up the beach when the 

 water is low. And these journeys are not infrequently 

 over surfaces sometimes comparatively slight in pitch. 



