THE PRESIDENT'S ADDRESS. 223 



the mouth of the flying-fish are so large as to fill up the greater 

 part of the cavity. Another Isojiod, the Icthyoxenus yellinghausu, 

 hollows out a comfortable residence for himself and his wife in the 

 coats of the stomach of one of the cyprinoid fishes. The crustacean 

 is said to penetrate from the outside, behind the abdominal fins, and 

 through the skin. The Pinnotheres, a crab, lives in the mussel and 

 other bivalves, and has been said to go out hunting, and bring his 

 meals home with him and share them with his host ; this probably 

 requires confirmation : if it be true, it certainly is quite opposed 

 to some of the definitions of a parasite. The barnacles are very 

 strange parasites. They do not usually want to feed on their host ; 

 they only want to be carried into good places where they may fish 

 for themselves ; and as creatures of this nature attach themselves 

 in such numbers to rocks, to ships, to floating wood, &c, it does 

 not seem very strange when we find some genera of them, as Tubi- 

 cinella, Coronula, Platylepas, and Chelonobia, adhering to whales, 

 sea-snakes, turtles, and even to the manatee ; but what does seem 

 odd is that as a rule a species of barnacle adheres to one species of 

 whale, and to that only. The Gallce also are cirrihipedes. They 

 are parasitic on crabs and lobsters, adhering to the abdomen, but 

 have become so degenerate from their parasitism that they have 

 but few organs left. 



One of the worms, Odontobius, which also only desires to pick 

 up passing scraps, seems to have a better idea of where to place 

 itself on the whale than the barnacle has, for it is found on the 

 whalebone, and a more favourable situation can hardly be imagined. 

 A polyp, Mnestra parasites, has a very quaint notion of how to 

 attain the same object, for it plants itself firmly on the head of a 

 gasteropod, Phyllirhoa bucephala, and it caused considerable dis- 

 cussion among zoologists when discovered. 



It is scarcely necessary to say that there are not any parasites, in 

 my sense of that word, among the higher vertebrata, for that sense 

 will not include either the vampire-bat, or the small Egyptian 

 plover which keeps the teeth of the crocodile clean, or the Pique- 

 bceuf, which seeks its dipterous prey on the back of the buffalo ; 

 but amongst fishes there certainly are cases very like parasitism ; 

 these are mostly very well known. The Ttemora attaches itself by 

 its suckers to a shark, or to some other fish which swims better 

 than it does itself. The fishes Fierasfer Hornei and Enchelyophis 



