344 



S. O. MAST 



moments, apparently very much excited; then they usually 

 swim two or three times entirely around the pool keeping very 

 close to the edge much as though they were looking for an out- 

 let; after this a number of them ordinarily crowd together and 

 wriggle well up on the beach into very shallow water. This 



Fig. II. Outline of a portion of a tide-pool with the outlet closed by means of 

 a board. This pool was 50 meters long, 13 meters wide and about 20 cm. 

 deep. It contained approximately 300 specimens of Fundulus, all but 75 of 

 which escaped to the sea by crossing a sand-bar 3 meters wide and fully 10 

 cm. high. T, tide-pool; o, outlet; S, sea; s, sand-bar; d, dam; r, ridge of sand; 

 p, small pool; c, m, n, x, y, points mentioned in the description. 



usually occurs in the original outlet at either end of the dam 

 across it. Finally one flops entirely out of the water onto the 

 sand. Others follow immediately much as sheep follow a leader. 

 After they have left the water they continue flopping and pro* 

 ceed directly across the bar which separates the pool from the 

 sea. (See Fig. I.) Those that are left ordinarily swim about 

 again for a few moments then collect as before, after which more 



