PHILOSOPHIC IGNORANCE. 59 



Great Britain and Ireland have a coast-line of more 

 than 4000 miles ; and of the more than 8000 fishes de- 

 scribed by naturalists 253 inhabit the fresh waters of Bri- 

 tain and the surrounding seas. Our shores abound with 

 those kinds of fish which exist in the largest numbers, 

 and yield a supply of the most grateful food. Our fish- 

 eries are an important branch of national industry, and 

 add largely to our national wealth ; so that a serious 

 diminution in their produce would affect the comfort of 

 all, and be ruinous to multitudes of our people. But 

 while we have such special reasons for investigating 

 the natural history of fishes, manifold are the difficulties 

 in the way of attaining the knowledge which we seek. 

 Dwelling in the depths of the ocean, or shunning obser- 

 vation in their favourite haunts in lakes and rivers, 

 they perform, unseen for the most part, the functions of 

 their being, so that there may be numerous species 

 whose very forms are yet unknown. Our philosophers, 

 moreover, as Goldsmith complained long ago, instead 

 of studying the nature of fishes, have too often " em- 

 ployed themselves only in increasing their catalogues, 

 from which all that results is but an additional tax on 

 our memory." The amount of philosophic ignorance 

 regarding the generation of fishes is curiously illustrat- 

 ed by the fanciful notions which prevailed as to that of 

 eels. Aristotle believed that they sprang from mud ; 

 Pliny maintained that they were propagated by frag- 

 ments separated from their bodies by rubbing against 

 rocks. Helmont asserted that they came from May- 

 dew, and gives this whimsical recipe for their produc- 

 tion : " Cut up two turves, covered with May-dew, and 

 lay one upon the other, the grassy sides inwards, and 

 thus expose them to the heat of the sun : in a few 

 hours there will be sprung from them an infinite quan- 

 tity of eels ! " Horse-hair from a stallion's tail, and 

 placed in water, used to be considered an unfailing 

 source for a supply of young eels ; a fancy which 

 lingered till the days of our youth, for we remember 



