Sullivan. — The Winter Flounder 133 



Observations on the young fish at rest strengthen this 

 belief. 



The fry are not strong swimmers, using "strong" to 

 convey the idea that they maintain themselves in motion 

 for long periods. It has often been remarked by those 

 handling the fry in the MacDonald jars that the fish are 

 found not only near the surface but throughout the en- 

 tire depth of the dish, due to the fact that their swim- 

 ming is spasmodic. Observation shows that the young 

 fishes will suddenly cease swimming and sink to the bot- 

 tom of the dish. After a short rest they will swim toward 

 the surface again. We may use a typical case from a 

 series of observations to illustrate this point. A fish of 

 eight days was kept under observation for a period of 

 ten minutes. During that period it stopped swimming 

 twenty-three times. Five times it came to rest on the 

 bottom of the dish ; the other times it resumed swimming 

 before reaching the bottom. After the observation the 

 fish was kept in continuous motion for thirty minutes and 

 at the end of the period showed no signs of fatigue. The 

 intermittent swimming is characteristic of the fry and 

 is not due to fatigue. 



In the younger fishes, those under ten days, preference 

 is shown to neither side when they come to rest. Ex- 

 tended observations on a large number of fry, taken 

 either as individuals or in groups, showed that in a given 

 number of times they would come to rest on the right side 

 fully as often as they did on the left. This statement 

 refers only to the cases where a large number were ob- 

 served for a long period, a period of not less than an hour, 

 or where an individual was kept under observation for a 

 longer time. My first impression, gathered from casual 

 observation in isolated cases, was that the fry favored the 

 left side during this earlier period. After the tenth or 

 twelfth day there is a tendency to favor the left side, and 

 a fish of two weeks will come to rest on that side seventy- 

 five times out of one hundred. Even after the eye migra- 

 tion has proceeded for some time the fish will occasionally 

 come to rest on the right side. All of this, however, I 



