8 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



organs occupying almost the whole of its body, each 

 composed of similar piles of thin plates arranged in 

 columns. Still another fish was known to have the power, 

 the Malapterurus found in the rivers of Africa; when 

 examined anatomically its thick skin was seen to consist 

 of piles of plates, each pervaded with innumerable sub- 

 dividing nerve-fibres. Organs thus built up and possessing 

 these properties were termed from their function Electric 

 Organs. 



Now it was felt by Mr. Darwin (and indeed is still felt 

 by all Biologists) that the rare possession by fish of organs 

 so complicated yet so effective, was a formidable fact which 

 the theory of Natural Selection was unable adequately to 

 grapple with. In what way could such organs have come 

 to be in the possession of these special fish and their 

 descendants ? Surely their near relations might be reason- 

 ably expected to have them also. 



The common Skate is such a near relation of the Torpedo 

 from the point of view of descent. Mr. Darwin therefore 

 suggested that it should be examined for the purpose of 

 ascertaining whether such an organ existed in it. In 1861 

 McDonnell of Dublin* announced the discovery of such 

 an organ. Upon what grounds ? These two only; first, 

 that in the same anatomical situation as in the case of the 

 Torpedo, there was a mass of substance containing columns 

 and an extensive nerve supply, and secondly, that on 

 histological examination this structure had a large number 

 of separated tubes with a large number of nerve endings. 

 He jumped at the conclusion that the organ was an 

 electrical one and Mr. Darwint accepted that conclusion. 

 But they had jumped into the abyss. The organ was not 

 an electrical one. The same mistake had been made in 



* McDonnell. Electric organs of the Skate. Nat. Hist. Review, p. 59. 

 t Darwin. Origin of Species, (p. 150, 6th edition). 



