32 THE COMMERCIAL SEA FISHES OF 



Spiny-rayed fish under the influence of anger or fear at 

 once erect their spiny rays, or even if unable to escape in 

 any other way have been known to attack their would-be 

 captor with their teeth. Fear is very apparent among 

 some marine forms of fishes. Porpoises and whales have 

 been observed to drive large schools of herrings and pil- 

 chards up estuaries, inside coves, or even direct upon the 

 sea-beach. 



Wounds inflicted by fish may be poisonous, or so in- 

 tensely irritating, that it becomes difficult to decide whether 

 such is or is not due to the presence of venom. Wounds 

 may be inflicted and severe, due to the presence of a highly 

 irritating substance existing on the surface of the spine by 

 which the injury has been inflicted, or else by a distinct 

 venom secreted by the fish, and ejected into the wound. 

 Or a jagged wound may be caused into which irritating 

 substance has been drawn by a toothed spine. Among 

 bony fishes it is not unusual for transient poisonous effects 

 to be produced from the puncture of a smooth-spined fin 

 ray, perhaps due to the property of the mucus which is 

 usually present. Some fish evidently secrete a venom, and 

 discharge it into a wound. This is effected by spinous fin 

 rays or spines situated on the head. (See weever fish, p. 79.) 

 i Fishes are dioecious, the sexes being normally found in 

 different individuals ; in exceptional instances hermaphro- 

 dites have been detected. Some forms are monogamous, 

 but the majority are polygamous, while the females are 

 usually more numerous than the males. In the sharks and 

 rays a congress occurs between the two sexes, and the 

 arrangement of the sexual organs is somewhat similar to 

 what obtains among the higher vertebrata. The ova, which 

 are few, are fertilised while still contained within the .ovi- 

 duct, and the development of the young is almost com- 



