454 GERTRUDE MAREAN WHITE 



obtained in July, August, January, February, March, and April, 

 since during the summer and winter months the fishes were less 

 restless and came for food more readily. That better results 

 were not always recorded for experiments during the fall might 

 be due to the fact that fishes were usually obtained in Sep- 

 tember and early October and were not yet adjusted to labora- 

 tory conditions. 



In the middle of April, May, and early June a marked rest- 

 lessness was noticed— often the fishes ate erratically and were 

 unfit for experunental work. It hardly seems probable that this 

 was due to a rise in temperature, as the fishes had been kept in 

 a room at ordinary temperature during the winter, and a series 

 of experiments had been carried on successfully during the hot- 

 test weeks of the summer. It was probably due to breeding 

 activities. The breeding season of the mudminnow comes dur- 

 ing the spring after the ice leaves the creeks and ponds where 

 they live. The fishes which have been confined in the laboratory 

 during the winter rarely, if ever, mature eggs, but there is prob- 

 ably a change in the gonads at this season. Two fishes which 

 had been accustomed to eat daily from forceps during the winter 

 months became restless in the spring, eating very irregularly, 

 but in July and August were again available for experiment. 



The mudminnow was the subject of a series of observations 

 on daily rhythm of activity. Across one corner of a room was 

 hung a large opaque window shade. In this a hole was cut three 

 inches square and about three feet from the floor. A table 

 was placed in front of the curtain in such a position that vessels 

 containing fishes could be seen by the observer who was seated 

 behind the curtain. The space behind the curtain was dark- 

 ened, and the observer kept as quiet as possible so that her 

 movements might not disturb the fishes. The vessels con- 

 taining the fishes w^ere always allowed to remain on the table 

 several hours before observations were made. During the hours 

 of the day and night, the movements of individual fishes within 

 the tanks were carefully mapped out on paper with as much 

 minuteness as possible, and the amount of time spent in each 

 position recorded with a stop-watch. 



