204 



BRANCH CHORDATA 



The function of the nostrils is smeUing and not breathing. 

 For none of them, except those in the hag-fish and lung fish, open 

 into the mouth. The odors must come through the water. All 

 fishes proper have two nostrils. Experimental proof of smell is 

 lacking, but the well-developed olfactory lobes and nerves argue 

 that the sense cannot be entirely wanting. 



Emotions. — If you have ever tried the sport of fishing with 

 hook and line, you know that fishes have emotions of fear and 

 curiosity. Romanes says they have also those of play, anger, 

 pugnacity, and jealousy. In some species parental affection is 

 proved by the building of nests (Fig. 163) and the care of the 

 young; sexual feelings, by courtship; social or gregarious in- 

 stincts, by their "schools."^ 



Fig. 164.— Sawfish. 



Upper, profile view. Lower, 



{Pristis pedinatus.) 



view of under part. 



Means of Defense. — Fishes most often protect themselves 

 from their enemies by their close resemblance to the surround- 

 ings, or by their swift movements, darting away at the least in- 

 timation of danger. But many are also armed with weapons 

 of defense, such as the spines connected with the fins of the dog- 

 fish and the catfish. The mucus which flows over the spines 

 is somewhat poisonous, making the wound painful. The 

 " Scorpanoids" have a little poison sac on each side near the tip 

 from which the poison flows down a groove of the spine into the 

 wound. The Thallassophryne has, besides the dorsal hollow 

 poisonous spines, in which the poison sac is situated at the base, 

 non-poisonous spines on the gill-covers. The porcupine-fish 

 {Di'odon macula'ta) and the globe-fish {Chylomyc' terus geome'tri- 

 cus) have spines all over the body. The "surgeons" and rays 

 ^ Baskett. 



