8 BULLETIN OF THE 



the curved condition is abnormal, and its appearance in the fishes raised 

 by Mr. Agassiz was probably owing to insufficient nutrition. The con- 

 trol of the pectorals in the case of this escaped fish was not lost, although 

 somewhat impaired. The fish was also able at once to execute vigorous 

 though ill-planned motions with the tail, and was therefore able to swim 

 rapidly, but in a reckless manner. The control of the caudal filament, 

 however, was entirely lost ; there was not the least trace of the rapid 

 vibratory movement, even when the pectorals were in active motion. By 

 the following day the use of the caudal filament had been partially re- 

 gained ; but its vibrations were rather feeble, and were resumed only 

 after long intervals of repose. 



The temperature of the water greatly affects the power of locomotion, 

 and very cold water may even produce fatal results in a comparatively 

 short time. In the summer of 1882 I placed a dozen or more fishes in 

 the cold water of a spring ; within twelve hours half of them were dead. 

 The first signs of an abnormal condition are shown by uncorrelated 

 movements, reckless swimming, and the inability to keep the dorso- 

 ventral axis vertical. The appearance is as though the centre of gravity 

 were located above the centre of volume, and the fish gradually became 

 incapable of remaining in its normal position of unstable equilibrium. In 

 swimming the body rolls from side to side. After a time the fish sinks 

 to the bottom of the vessel, and can regain the surface only with consid- 

 erable exertion ; it cannot remain at the surface in a motionless condi- 

 tion. At length the body usually becomes curved sidewise. In this 

 condition the fish may remain for many hours, or even several days. 

 Restoration to fresh water of the ordinary temperature seems to have 

 only a temporary effect, or none. The only way to afford relief is to 

 place the fishes in direct sunlight until the water becomes warm, when, 

 if not already too much affected, they will gradually recover. 



The movements of the eyes are principally in the horizontal plane. 

 When one eye is directed obliquely forward, the other looks obliquely 

 backward at about the same angle, so that the axes of the two eyes 

 are kept approximately parallel. 



The manner in which young gar-pike capture and swallow their prey 

 is interesting, and serves to show why it is so difficult to get them to 

 feed on anything except living objects. When very young, as previously 

 stated, they will not feed on anything but mosquito larvae. The fish 

 always approaches the larva by a slow, even motion, resulting from the 

 vibration of the pectorals and the tip of the tail, until the prey is about 

 opposite the middle of the "bill"; then with a quick lateral motion of 



