350 S. O. MAST 



these animals overland to the sea. Vision of the sea seems to 

 play little or no part in this, for the fishes continue toward the 

 sea if a screen is so placed that the water can not be seen; or if 

 conditions are so arranged that the largest surface of water 

 visible is in the tide-pool. The slope of the beach can also not 

 serve to guide them, for in crossing the sand-bar they have 

 to go up grade as well as down. Nor are there any other external 

 features that seem capable of serving as a guide. The phenom- 

 enon is consequently probably very largely dependent upon 



internal factors. 



SUMMARY 



1. Fundulus is frequently found in temporary tide-pools, 

 but rarely if ever after the water is so low that the outlet is 

 closed. When the tide is falling it swims out and in at short 

 intervals but as soon as the water in the outlet gets low it does 

 not return. In this way it avoids being caught in these pools 

 and killed when they dry during low tide. 



2. If the outlet is closed while the tide is rising nothing 

 out of the ordinary occurs, but if it is closed while the tide is 

 falling the fishes swim about rapidly in various directions for 

 a few moments. Then they come out of the water and travel 

 overland to the sea. Many specimens have been seen thus to 

 leave large tide-pools and travel across sand-bars more than 

 3 m. wide and 10 cm. high. 



3. Fundulus nearly always leaves the pools on the sea side 

 near the original outlet. It apparently remembers the location 

 of the outlet ; and it is the sudden closing of this that constitutes 

 the principal factor causing these fishes to leave the pools. 



4. On land they never travel in the wrong direction any 

 considerable distance. It is not known how they are guided 

 in the right direction, but it is known that light reflected from 

 the water is not a significant factor in the process. 



5. Locomotion on land is brought about by successive leaps 

 due to rapid bending of the body. The course taken is fairly 

 direct. Every leap carries the animal in the right direction, 

 although the ax'al position at the beginning of the successive 

 leaps varies greatly; the fish, at this time, may be headed in the 

 direction of locomotion or in the opposite direction or in any 

 other direction. The movements appear to be well coordinated, 

 but the process involved in thus regulating the direction of 

 locomotion is not understood. 





