10 TRANSACTIONS LIVEEPOOL BIOLOGICAL SOCIETY. 



Acad., 1888, VII, page 301, and Ewart: Transactions of 

 Eoyal Society, Edin., 1892). 



Seventeen years before McDonnell's mistake Dr. Stark, 

 of Edinburgh, discovered in the same fish (Baia batis), but 

 in quite a different situation (in the long tail of the Bay) 

 an organ with piles of plates arranged in columns and 

 with a very extensive nerve supply. He inferred from its 

 structure that it was an electrical organ, but was careful 

 to say that he had no evidence except its anatomical 

 resemblance to the powerful active organs of the Torpedo.* 

 This organ was examined later as to its function and was 

 found to be capable of generating electrical currents of 

 considerable intensity, though not strong enough to be 

 perceptible to a man's hand, except perhaps in the case of 

 very large fish. Stark's inference was sound, because in 

 this case the function, when investigated, was found to be 

 that which the structure led its discoverer to predict. 



Since then a number of fish in the Nile, one especially 

 the Mormyrus, have been found to have similarly con- 

 structed organs, but for a long time these were termed 

 pseudo-electric organs. They have now been examined 

 by physiological methods, and undoubted evidence of 

 electrical changes of considerable intensity has been 

 obtained. They are theiefore true electrical organs. 



It is worthy of note that in both this case and the skate, 

 we should never have got at the function but for the 

 discovery of the structure. These are instances of like 

 function being inferred from like structure and they 

 illustrate at once the great value of the structural resem- 

 blance in guiding us to a true functional interpretation, 

 and the dangers which the inference involves when 

 unsupported by physiological inquiry. 



* Stark. Proceedings Royal Soc, Edinburgh, Vol. II, No. 25. This 

 discovery appears to have been disregarded for many years. 



