348 S. O. MAST 



The results show, moreover that after the fishes are out on the 

 land they tend to go directly toward the sea. This is evident 

 from the persistent attempts made in experiment 1, to cross 

 the ridge at y, and from the direct course taken after passing 

 the ridge, especially in the small pool p. They show, further- 

 more, that the tendency to go toward the sea is not a response 

 to the light reflected from the water, for in experiment 1, the 

 fishes, when they were behind the ridge, persistently attempted 

 to go toward the sea, although in this position, the ridge effect- 

 tively hid the sea from view while the pool was fully exposed. 

 In experiment 2 they also proceeded toward the sea under 

 similar conditions, or rather toward the original outlet of the pool. 



3. As previously stated, if the tide flows in when the pool 

 is closed, nothing out of the ordinary occurs in the reactions 

 of Fundulus. Only in one experiment, that described below, 

 was there an exception to this. Unfortunately, owing to other 

 duties, I was unable to repeat this experiment under the same 

 conditions. 



On September 7, at 10.19 A. M. the outlet of a large tide-pool 

 (12 by 30 m.) containing about 350 funduli was closed. At 

 this time there was a strong current of water running into the 

 pool indicating that the tide was still rising. Immediately after, 

 the pool was closed, the fishes began to swim about rapidly 

 being apparently very much excited, and two minutes later 

 they began to come out of the water. In short, they behaved 

 precisely as they ordinarily do when the tide is running out, 

 not at all as they ordinarily do when it is running in. They 

 continued to come out for some time, most of them, as usual 

 near the original outlet, but nearly all of them returned to the 

 pool ; only a few succeeded in crossing the sand-bar which separ- 

 ated the pool from the sea. The sun was very hot at this time 

 and the sand on the bar rather dry. This probably accounts 

 for the fact that nearly all returned to the pool after proceeding 

 a short distance toward the sea. At 10.40 the tide had un- 

 questionably turned for the water outside the pool was already 

 several centimeters lower than that inside. The tide was con- 

 sequently very nearly high when the pool was first closed and 

 this no doubt, was the cause of the unusual behavior. If this 

 is true it must be assumed that in some way these animals know 

 when the tide is about to turn, for their method of response 



