114 The Life Story of the Fish 



inside of the skull which they are sure harbored the cranial 

 elements of what must have been an olfactory apparatus. 



In the present-day fishes the receptors of smell are lo- 

 cated, like ours, in the nostrils, but the nostrils are not like 

 ours. They are little holes in the top of the snout, but instead 

 of connecting with the throat by a passage, they open into 

 small blind sacs just under the skin, and go no further. The 

 sacs are lined with the organs of smell. There are two such 

 sacs, one on each side of the snout, and in most fishes there 

 are two external openings, two nostrils, one behind the other, 

 connecting with each sac. To bring the water carrying the 

 odors into the sac where the organs are, there are either 

 muscles, or little moving hairs called cilia, which keep a 

 current flowing in the front opening and out the rear. 



The fish's tongue is a flat cartilaginous and gristly projec- 

 tion from the floor of the mouth. It has no muscles, and it 

 cannot move, but it does have taste-buds which experiment 

 has proved do distinguish between at least some of the flavors 

 which our taste-buds sense. Many fish are insensitive to sweet 

 flavors, perhaps because, as our experience indicates, few 

 things from under the water taste sweet; but many species 

 have an acute sense of sour, salt, and bitter. 



We are all aware of the fact that taste and smell are closely 

 related. The principal difference is that we can smell things 

 at a distance, while we can taste things only when we are 

 in contact with them. The explanation of this is that the 

 tongue must have a much stronger stimulus than the nostrils. 

 The very small amount of material that reaches us through 

 the air from a distant body will form a solution on the moist 

 surfaces of both, but it is too dilute to have any effect on 

 the tongue, and only the nostrils register it. The sense of 

 taste appears to have been designed to tell animals whether 

 what they have taken into their mouths is edible or not. What 

 tastes good is, in general, good to eat. The sense of smell is 



