10 BULLETIN OF THE 



end of the prey is thus brought to lie in the gar-pike's throat, which is 

 often greatly distended by it. The movements by which the shifting of 

 the minnow is accomplished are rather complicated, and require a nice 

 correlation to be successful. During the process of transferring it cross- 

 wise between the jaws, the latter have to be opened quickly, and this 

 motion is instantly followed by a quick lateral motion of the whole head 

 in the proper direction. This lateral motion is accompanied by two 

 others ; one a forward thrust of the whole body, and the other a de- 

 pression of the floor of the mouth. To accomplish the first movement 

 there is a preparatory curving of the post-anal portion of the body, the 

 sudden straightening of which at the instant the jaws are loosened gives 

 the necessary forward impetus, and helps to prevent the escape of the 

 prey ; this is further guarded against by the second motion, — the de- 

 pression of the floor of the mouth. The gill covers being in contact 

 with the sides of the body, this latter motion produces a tendency to a 

 vacuum in the mouth, which can be satisfied only by a sudden influx of 

 water between the jaws. The current thus produced of course has the 

 effect of carrying with it any movable object in the mouth or its imme- 

 diate vicinity, and of impeding the escape of the prey until the jaws are 

 again closed upon it. While the hold upon the prey is gradually shifted 

 from its tail region to its head region, the part of the jaws which holds 

 it is also not the same as at first. By the time the fish has been fully 

 shifted laterally, it will be very near the base of the jaws, for at each 

 loosening of the latter they have been thrust forward a little by the 

 motion of the whole body. But that is not all, for when the prey has 

 been shifted back to near the base of the jaws, — as one can see better 

 in the case of the larger gar-pikes, — each subsequent movement of the 

 latter causes the prey to take a slightly different direction, so that it is 

 finally swung around until it is parallel with the jaws instead of cross- 

 wise to them. I am not entirely certain how this is effected ; but it is 

 all accomplished when the fish is held in the jaws near their base. It 

 is possible that the teeth of one ramus of the jaw are not loosened quite 

 as promptly as those of the other, and that as a consequence they act 

 for an instant as a sort of pivot for the rotation of the prey. But that 

 both sides of the jaw are ultimately set free at each motion is probable, 

 from the great liability of the prey to escape at this very critical step in 

 the process. Or it may be that the lower jaw is moved slightly toward 

 one side as the jaws are being opened, thus giving a swing to the prey 

 which changes its axis slightly before it is again caught by the closing 

 jaws. Whatever the means by which it is effected, it is certain that 



