FISHES l6l 



this way it can, and often does, kill such vigorous fast- 

 swimming fishes as the Salmon and Sea Bass. 



Certain South American Catfishes (Pjgidiidae) attach 

 themselves to other fish or even large animals entering 

 the water, piercing the skin and drinking the blood, much 

 as the Vampire Bat attacks its victim. Some allied forms 

 enter the gill cavities of large fishes and use both teeth 

 and sharp spines to excite a blood flow from their un- 

 willing host. 



The only other case of parasitism is that of a deep-sea 

 Angler referred to later. Here the parasitism is rather of 

 a commensal nature since the race depends upon the male 

 quartering himself upon his gigantic spouse and tapping 

 her bloodstream for his own immediate sustenance. 



False parasitism is that wherein two widely different 

 creatures live together for the joint well-being, forming 

 as it were a co-operative society. The only instance met 

 with in marine fishes is that wherein colonies of Hydroids 

 attach themselves to certain fishes, thus warding off foes 

 and at the same time catching minute scraps of food dis- 

 carded by the fish when eating. 



Partnerships in which the tenant comes and goes at will 

 without conferring any special benefit on its landlord 

 or protector are not uncommon. A remarkable instance 

 is that of the Florida Cardinal Fish (Apogomchtbjs). It 

 lives in the mantle cavity of the Sea Snail known as the 

 Fountain Shell, the fish entering and leaving its host at 

 will, causing no little inconvenience. Several species of 

 Goby enter Sponges, using the sharp jaws and bi-lateral 

 series of scales to climb up and down the long tunnels 

 of the Sponge's interior. 



