2 7 8 



ment more rapidly in an aquarium when supplied with 

 suitable nourishment than they do in the open sea. Thus 

 in the Southport aquarium some about three inches across, 

 increased in two and a half years to 10 Ib. in weight, and 

 after two years more they further augmented to 20 Ib., or a 

 yearly average in amount of 4J Ib. a fish. 



In marine fisheries the question of the food upon which 

 the various forms of fish subsist is of vital importance, as 

 on it greatly depends whether legislation might be reason- 

 ably expected to prove useful, superfluous, or mischievous. 

 Many forms are omnivorous, others carnivorous, and a few 

 herbivorous. Some, like the sucking fish Remora, attach 

 themselves to the bodies of whales, sharks, and larger fishes 

 and so are carried about by their host, upon whom they 

 do not prey, but simply use him as a means of conveyance, 

 and these are termed commensals. Others, as the borer 

 or hag, Myxine glutinosa, is a true parasite, attaching itself 

 to another fish, into which it bores and devours, sub- 

 sequently passing on to fresh victims. Some fishes, as the 

 pilot fish, Naucrates ductor, or the black fish Centrolophus 

 pompilus, would seem to keep company with whales, sharks, 

 sun fishes, and other forms, mostly for the purpose of sub- 

 sisting upon the parasites which infest these larger species, 

 or to obtain their excrementitious dejections. The lamprey, 

 besides attacking living fish, likewise prey upon such 

 as are in an advanced s^age of putrefaction, and many 

 forms will not only devour the eggs and young of their 

 neighbours, but likewise those of their own species. In a 

 sturgeon's stomach Thompson observed several examples 

 of minute crustaceans (A mphipoda), the remains of shrimp- 

 like forms, fragments of Porphyra, which had probably been 

 growing on the sandy bottom of the sea, and a perfect, but 

 minute Tellina tenuis ; it likewise contained some fine sand, 

 with which the intestines were wholly filled. The Polyodon 



