1 70 Popular Delusions in Natural History. [Sess. 



facts may in consequence become inconceivably distorted in 

 the mind of the individual so affected. It is dangerous to 

 talk of fads, as there is scarcely one of us that has not his 

 own little weakness in this direction, so one instance may 

 suffice. Many well-meaning people may come to have their 

 minds so seriously biassed as to the supposed moral wrong of 

 taking away life in animals, that they actually come to believe 

 and to preach that the use of animal food is the one great 

 cause of nearly all the evil passions as well as most of the 

 bodily diseases to which frail humanity is subject ! 



Popular delusions on matters of Natural History have been, 

 and are still, so extremely numerous, that we can only deal 

 this evening with a few selected cases. They are not confined 

 to any particular class or order of animals, but the Vertebrata 

 certainly furnish us with by far the greater number of 

 examples. 



As to the Invertebrata, we need only mention the case of 

 evolution extraordinary which is, by the common people in 

 many parts of the country, thought to take place when a horse- 

 hair is left in a stream or lake for a little while. It assumes 

 life, begins to move and to swim about, and finally it evolves 

 into an eel. This is surely more remarkable than the evolution 

 of man from a pithecoid ancestor ! The origin of this idea 

 has long been settled as attributable to the Gordius aquaticus, 

 a long, slender, almost hair-like worm which lives part of its 

 life in water, part as an internal parasite in the bodies of 

 insects. Here we have, in the first place, a case of faulty 

 observation in mistaking a worm for a horse-hair ; in the 

 second, the utterly unwarrantable supposition that this moving 

 hair-like body afterwards becomes an eel ; thirdly, the con- 

 version of this fancy into a supposed actual fact, and its being 

 spread about from mouth to mouth and generation to genera- 

 tion as an accepted popular belief. This is a typical case of 

 a popular delusion. 



We may allow this example to stand for the Fishes as well 

 as for the Invertebrata, and pass to the Amphibia, concerning 

 which there were, and to some extent still are, some strange 

 delusions current among the people. The case of the frogs 

 and toads supposed to be found alive in the interior of blocks 

 of stone we shall consider under the head of Geology ; here 



