PROTRACTILE MOUTHS 



compels the upright branch of the premaxilla to rise 

 and fold back, the horizontal branch to slide towards 

 the orbit, the various parts to come together and 

 close up, and as the tube disappears with the closing 

 of the jaws, there is only a slit-like orifice, a trap-like 

 mouth, and the ordinary snout of a fish. 



I carry out these backward and forward movements 

 on a dead specimen, the thrusting forth of the tube 

 and its subsequent withdrawal, and I pass slowly 

 from one to the other the better to observe the suc- 

 cessive stages. But what a difference there is between 

 this slow operation and what happens when the 

 creature is fully alive, swimming upright in deep 

 waters. The projection and withdrawal take only an 

 instant. Suddenly the creature opens its mouth — it 

 takes no longer to do so than any other fish — and, at 

 the same time, without any delay, the mechanism gets 

 to work; its parts stretch out and separate and the 

 snout is immediately formed into a large protruding 

 tube. Then, with equal rapidity, the mouth closes; 

 everything folds up, goes back upon itself, and returns 

 to the normal position of rest. We cannot help seeing 

 the resemblance to a mask. In the normal state, there 

 is nothing of all this to be seen from outside. The 

 mechanism is hidden behind a mask and appears only 

 at certain moments. Then the creature presents an 

 appearance previously unsuspected, and of which there 

 was no sign. 



This protractile mouth helps in the business of 

 securing food. The large tube, thus projected, is 

 used by the dory every time it wishes to seize 

 its prey. Like other fishes, it opens its mouth to snap 

 up its victim, but it does more than this; it stretches 

 out the mouth and lengthens it, so that it can grasp 

 the victim and seize it more surely. It has teeth too, 

 but they are small and not many: they do not help it 

 very much. The main part in the prehensile function 

 is played by the mouth and its power of projection, 

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