296 



THE AMERICAN NATURALIST 



[Vol. XLI 



(1) A skate was put into a rectangular glass vessel measuring 

 about 12 by 18 inches, containing sea water to the depth of about 

 3 inches. The fish was allowed to become quiet and then was left 

 undisturbed for two hours, during which time a copious stream 

 of water was flowing into the vessel. At the end of this period 

 the animal was found resting quietly, respiration being at the rate 

 of 22 per minute, while spouting occurred at very irregular intervals 

 averaging about 1^ minutes. 



The stream of running water was now shut off and the fish was 

 left in the vessel without change of water for about three hours. 

 During the earlier part of this time there were alternate periods 

 of quiet and unrest. In one of the periods of quiet, the respiration 

 was slow and the spiracle was only slightly opened. But after a 

 minute or two of these resting conditions, respiration became 

 markedly quickened, the spiracle being opened wide at each 

 inspiration, and shortly the fish raised its head and began to swim 

 about, usually trying to swim up the low vertical side of the aqua- 

 rium so that the head was thrust out of the water. This activity 

 lasted usually less than a minute, after which the fish dropped to 

 the bottom of the aquarium and became quiet, the respiration at 

 once slowing down to the normal resting rate. Sometimes the 

 performance was varied in that the quickened respiration which 

 marked the close of an interval of rest was followed, not by the 

 swimming activity, but by a vigorous spouting, after which slow 

 respiration was resumed. At still other times the period of unrest 

 was marked by both the swimming and the spouting. Occasion- 

 ally the spouting occurred also in the resting intervals. 



During the second hour after the incurrent stream of water 

 was shut off the alternate periods of rest and unrest continued. 

 The rate of respiration, however, gradually increased, reaching 

 a maximum at the end of the second hour when the fish was 

 breathing 59 times per minute and spouting about once per min- 

 ute. Respiration was equally rapid during rest and unrest. The 

 activity was often much more violent than in the first hour of the 



in the third hour of the <-\[)('riiii('iii thr rate of respiration 

 diniinisluMl with increasing rapidity. Following is the record 

 (the rimning water having been shut off at l.()0 P. M.). 



