LARVAL FISHES : THEIR METAMORPHOSES. 131 



transmuted into its living prototype, the "hair- 

 eel," and this, by continuous growth, might in 

 turn become the true eel. When the belief that 

 non-living matter could, under certain con- 

 ditions, beget living organisms, was shown to 

 be untenable, the source of origin of the common 

 eel became more mysterions than before. And 

 a mystery it remained until the year of Grace 

 1864. In that year Mr Gill read to us the riddle 

 of all the ages, at least since Aristotle. He showed 

 us that some forms at least of certain curious, rare 

 and very delicately framed fishes, which had long 

 been a stumbling-frock to scientists, were none 

 other than the long-sought-for larval eels. They 

 had already received the name of Leptocephali, 

 but were regarded as monstrosities, the victims 

 of uncongenial surroundings. Thus Dr Giinther, 

 one of the most profound authorities of our time 

 on all matters pertaining to fishes, wrote of 

 them: "We must come to the conclusion that 

 the Leptocephalids are the offspring of various 

 kinds of marine fishes, representing not a normal 

 stage of development (larvae), but an arrest of 

 development at a very early period of their life ; 

 they continue to grow to a certain size without 

 corresponding development of their internal 

 organs, and perish without having attained the 

 characters of the perfect animal." A year after 

 this was written Dr Giinther himself was enabled 

 to add further confirmation of Mr Gill's discovery. 

 But it was not till 1896 that certain Italian 

 naturalists, by a very careful and exhaustive 

 study of a large series of Leptocephalids were 

 enabled to establish beyond fear of dispute, that 



